Australian Journal of Zoology Australian Journal of Zoology Society
Evolutionary, molecular and comparative zoology
RESEARCH ARTICLE

Using phytohaemagglutinin to determine immune responsiveness in saltwater crocodiles (Crocodylus porosus)

John W. Finger Jr Jr A B F , Amanda L. Adams D , Peter C. Thomson B , Cathy M. Shilton D , Greg P. Brown E , Christopher Moran B , Lee G. Miles B , Travis C. Glenn A and Sally R. Isberg B C

A Department of Environmental Health Science, University of Georgia, 150 Green Street, Athens, GA 30602, USA.

B Faculty of Veterinary Science, University of Sydney, Sydney, NSW 2006, Australia.

C Centre for Crocodile Research, PO Box 329, Noonamah, NT 0837, Australia.

D Berrimah Veterinary Laboratories, GPO Box 3000, Darwin, NT 0801, Australia.

E School of Biological Sciences, University of Sydney, Sydney, NSW 2006, Australia.

F Corresponding author. Email: finger20@uga.edu

Australian Journal of Zoology 61(4) 301-311 http://dx.doi.org/10.1071/ZO13041
Submitted: 17 May 2013  Accepted: 5 August 2013   Published: 23 August 2013

Abstract

Immune responsiveness, the ability of an organism to effectively respond immunologically following antigenic exposure, is an essential component of life history, as organisms require effective immune functionality in order to grow, survive and reproduce. However, immune status is also associated with concomitant trade-offs in these physiological functions. Herein we demonstrate the validation of phytohaemagglutinin (PHA) injection in saltwater crocodiles, Crocodylus porosus, to assess cellular immune responsiveness. Following injection of 2 mg mL–1 PHA into the hind toe webbing, we observed a peak swelling response 12 h after injection, with PHA inducing increased thickness compared with webs injected with phosphate-buffered saline (PBS) (F5,518 = 145.13, P < 0.001). Subsequent injections increased responsiveness relative to the primary injection response (F5,290 = 2.92, P = 0.029), suggesting that PHA exposure induced immunological memory, a tenet of acquired immunity. Histological examination revealed that PHA-injected toe webs displayed increased numbers of leukocytes (granulocytes, macrophages, and lymphocytes) relative to PBS-injected webs, with peak leukocytic infiltrate observed 12 h after injection. We suggest the use of PHA injection in crocodilians as a measure of cellular immune responsiveness in agricultural (production and animal welfare), ecological, and toxicological contexts.

Additional keywords: agriculture, crocodilian, ecology, toxicology.


References

Abbas, A. K., Lichtman, A. H., and Pillai, S. (2010). ‘Cellular and Molecular Immunology.’ (Elsevier: Philadelphia.)

Bascuñán-García, A. P., Lara, C., and Córdoba-Aguilar, A. (2010). Immune investment impairs growth, female reproduction and survival in the house cricket, Acheta domesticus. Journal of Insect Physiology 56, 204–211.
Immune investment impairs growth, female reproduction and survival in the house cricket, Acheta domesticus.CrossRef | 19840805PubMed | open url image1

Bonato, M., Evans, M. R., Hasselquit, D., Cloete, S. W. P., and Cherry, M. I. (2009). Growth rate and hatching date in ostrich chicks reflect humoral but not cell-mediated immune function. Behavioral Ecology and Sociobiology 64, 183–191.
Growth rate and hatching date in ostrich chicks reflect humoral but not cell-mediated immune function.CrossRef | open url image1

Boughton, R. K., Bridge, E. S., and Schoech, S. J. (2007). Energetic trade-offs between immunity and reproduction in male Japanese quail (Cortunix coturnix). The Journal of Experimental Zoology 307A, 479–487.
Energetic trade-offs between immunity and reproduction in male Japanese quail (Cortunix coturnix).CrossRef | 1:CAS:528:DC%2BD2sXhtVOrsbzJ&md5=0cc98a279f5310dc163edd947a1ecf92CAS | open url image1

Brown, G. P., Shilton, C. M., and Shine, R. (2011). Measuring amphibian immunocompetence: validation of the phytohemagglutinin skin-swelling assay in the cane toad, Bufo marinus. Methods in Ecology and Evolution 2, 341–348.
Measuring amphibian immunocompetence: validation of the phytohemagglutinin skin-swelling assay in the cane toad, Bufo marinus.CrossRef | open url image1

Brzek, P., and Konarzewski, M. (2007). Relationship between avian growth rate and immune response depends on food availability. The Journal of Experimental Biology 210, 2361–2367.
Relationship between avian growth rate and immune response depends on food availability.CrossRef | 17575041PubMed | open url image1

Caipang, C. M. A., Brinchmann, M. F., Berg, I., Iversen, M., Eliassen, R., and Kiron, V. (2008). Changes in selected stress and immune-related genes in Atlantic cod, Gadus morhua, following overcrowding. Aquaculture and Research 39, 1533–1540.
Changes in selected stress and immune-related genes in Atlantic cod, Gadus morhua, following overcrowding.CrossRef | 1:CAS:528:DC%2BD1cXhsVWltrzJ&md5=39583bf1ae11c0c2b2a8535de7417458CAS | open url image1

Canfield, P. J. (1985). Characterization of the blood cells of Australian crocodiles (Crocodylus porosus [Schneider] and C. johnstoni [Krefft]). Anatomia, Histologia, Embryologia 14, 269–288.
Characterization of the blood cells of Australian crocodiles (Crocodylus porosus [Schneider] and C. johnstoni [Krefft]).CrossRef | 1:STN:280:DyaL287ls1yjug%3D%3D&md5=67cd419a729c5d749fdcf6e334881c3aCAS | 2420235PubMed | open url image1

Chen, X., Niu, C., and Pu, L. (2007). Effects of stocking density on growth and non-specific immune responses in juvenile soft-shelled turtle, Pelodiscus sinensis. Aquaculture and Research 38, 1380–1386.
Effects of stocking density on growth and non-specific immune responses in juvenile soft-shelled turtle, Pelodiscus sinensis.CrossRef | open url image1

Craighead, F. C. (1968). The role of the alligator in shaping plant communities and maintaining wildlife in the southern Everglades. Florida Naturalist 41, 2–7. open url image1

Demas, G. E., Zysling, D. A., Beechler, B. R., Muehlenbein, M. P., and French, S. S. (2011). Beyond phytohaemagglutinin: assessing vertebrate immune function across ecological contexts. Journal of Animal Ecology 80, 710–730.
Beyond phytohaemagglutinin: assessing vertebrate immune function across ecological contexts.CrossRef | 21401591PubMed | open url image1

Duffy, D. L., and Ball, G. F. (2002). Song predicts immunocompetence in male European starlings (Sturnus vulgaris). Proceedings of the Royal Society of London. Series B, Biological Sciences 269, 847–852.
Song predicts immunocompetence in male European starlings (Sturnus vulgaris).CrossRef | open url image1

Elsey, R. M., Joanen, T., McNease, L., and Lance, V. (1990). Stress and plasma corticosterone levels in the American alligator – relationships with stocking density and nesting success. Comparative Biochemistry and Physiology. Part A, Physiology 95, 55–63.
Stress and plasma corticosterone levels in the American alligator – relationships with stocking density and nesting success.CrossRef | open url image1

Fair, J. M., Hansen, E. S., and Ricklefs, R. E. (1999). Growth, developmental stability and immune response in juvenile Japanese quails (Coturnix coturnix japonica). Proceedings of the Royal Society of London. Series B, Biological Sciences 266, 1735–1742.
Growth, developmental stability and immune response in juvenile Japanese quails (Coturnix coturnix japonica).CrossRef | 1:STN:280:DyaK1Mvks1Gqsg%3D%3D&md5=47870a388cabe431180a9455d08e2044CAS | open url image1

Fairbrother, A., Smits, J., and Grasman, K. A. (2004). Avian immunotoxicology. Journal of Toxicology and Environmental Health Part B 7, 105–137.
Avian immunotoxicology.CrossRef | 1:CAS:528:DC%2BD2cXhtFCgsrw%3D&md5=b077aebaa1fb67a1b09bbeab703c06a2CAS | open url image1

Finger, J. W., and Isberg, S. R. (2012). A review of innate immune functions in crocodilians. CAB Reviews 7, 1–11.
A review of innate immune functions in crocodilians.CrossRef | open url image1

Fukuda, Y., Webb, G., Manolis, C., Delaney, R., Letnic, M., Lindner, G., and Whitehead, P. (2011). Recovery of saltwater crocodiles following unregulated hunting in tidal rivers of the Norther Territory, Australia. The Journal of Wildlife Management 75, 1253–1266.
Recovery of saltwater crocodiles following unregulated hunting in tidal rivers of the Norther Territory, Australia.CrossRef | open url image1

Glassman, A. B., Bennett, C. E., and Hazen, T. C. (1981). Peripheral blood components in Alligator mississippiensis. Transactions of the American Microscopical Society 100, 210–215.
Peripheral blood components in Alligator mississippiensis.CrossRef | open url image1

Grasman, K.A. (2002). Assessing immunological function in toxicological studies of avian wildlife. Integrative and Comparative Biology 42, 34–42.
Assessing immunological function in toxicological studies of avian wildlife.CrossRef | 1:CAS:528:DC%2BD3sXhs1yhtLY%3D&md5=2c715958f667d69463b919b19c5cb2d1CAS | 21708692PubMed | open url image1

Gutierrez, J. S., Abad-Gomez, J. M., Villegas, A., Sanchez-Guzman, J. M., and Masero, J. A. (2013). Effects of salinity on the immune response of an ‘osmotic generalist’ bird. Oecologia 171, 61–69.
Effects of salinity on the immune response of an ‘osmotic generalist’ bird.CrossRef | 22782496PubMed | open url image1

Hanlon, A. J., Rhind, S. M., Reid, H. W., Burrells, C., Lawrence, A. B., Milne, J. A., and McMillen, S. R. (1994). Relationship between immune response, liveweight gain, behaviour and adrenal function in red deer (Cervus elaphus) calves derived from wild and farmed stock, maintained at two housing densities. Applied Animal Behaviour Science 41, 243–255.
Relationship between immune response, liveweight gain, behaviour and adrenal function in red deer (Cervus elaphus) calves derived from wild and farmed stock, maintained at two housing densities.CrossRef | open url image1

Hernandez, A., Yager, J. A., Wilkie, B. N., Leslie, K. E., and Mallard, B. A. (2005). Evaluation of bovine cutaneous delayed-type hypersensitivity (DTH) to various test antigens and a mitogen using several adjuvants. Veterinary Immunology and Immunopathology 104, 45–58.
Evaluation of bovine cutaneous delayed-type hypersensitivity (DTH) to various test antigens and a mitogen using several adjuvants.CrossRef | 1:CAS:528:DC%2BD2MXms1Knsw%3D%3D&md5=18d6662fdaa32a5d971112a5e1418463CAS | 15661330PubMed | open url image1

Isberg, S.R., Thomson, P.C., Nicholas, F.W., Barker, S.C., and Moran, C. (2004). Farmed saltwater crocodiles – a genetic improvement program. Rural Industries Research and Development Corporation Paper No. 04/147.

Isberg, S. R., Thomson, P. C., Nicholas, F. W., Barker, S. C., and Moran, C. (2005). Quantitative analysis of production traits in saltwater crocodiles (Crocodylus porosus): II. Age at slaughter. Journal of Animal Breeding and Genetics 122, 370–377.
Quantitative analysis of production traits in saltwater crocodiles (Crocodylus porosus): II. Age at slaughter.CrossRef | 1:STN:280:DC%2BD2Mrps1ertA%3D%3D&md5=d1b6f9de2188dffe2802f5c5de0ea21fCAS | 16274420PubMed | open url image1

Isberg, S. R., Thomson, P. C., Nicholas, F. W., Barker, S. C., and Moran, C. (2006). Quantitative analysis of production traits in saltwater crocodiles (Crocodylus porosus): III. Juvenile survival. Journal of Animal Breeding and Genetics 123, 44–47.
Quantitative analysis of production traits in saltwater crocodiles (Crocodylus porosus): III. Juvenile survival.CrossRef | 1:STN:280:DC%2BD28%2Fjtlarug%3D%3D&md5=429824ad6ead59aff434e79805a82634CAS | 16420264PubMed | open url image1

Isberg, S., Shilton, C., and Thomson, P. (2009). Improving Australia’s crocodile industry productivity – understanding runtism and survival. Rural Industries Research and Development Corporation Paper No. 09/135.

Keller, J. M., McClellan-Green, P. D., Kucklick, J. R., Keli, D. E., and Peden-Adams, M. M. (2006). Effects of organochlorine contaminants on loggerhead sea turtle immunity: comparison of a correlative field study and in vitro exposure experiments. Environmental Health Perspectives 114, 70–76.
Effects of organochlorine contaminants on loggerhead sea turtle immunity: comparison of a correlative field study and in vitro exposure experiments.CrossRef | 1:CAS:528:DC%2BD28XosVOjtw%3D%3D&md5=28b40b36b1eedf343d892ecff5a433e5CAS | 16393661PubMed | open url image1

Kennedy, M. W., and Nager, R. G. (2006). The perils and prospects of using phythohaemagglutinin in evolutionary ecology. Trends in Ecology & Evolution 21, 653–655.
The perils and prospects of using phythohaemagglutinin in evolutionary ecology.CrossRef | open url image1

Lance, V. A., and Lauren, D. (1984). Circadian variation in plasma corticosterone in the American alligator, Alligator mississippiensis and the effects of ACTH injections. General and Comparative Endocrinology 54, 1–7.
Circadian variation in plasma corticosterone in the American alligator, Alligator mississippiensis and the effects of ACTH injections.CrossRef | 1:CAS:528:DyaL2cXhtFyjtbw%3D&md5=ff51c6aa2c9bcb1a987b64fd8fcd800cCAS | 6327457PubMed | open url image1

Lutton, B., and Callard, I. (2006). Evolution of reproductive–immune interactions. Integrative and Comparative Biology 46, 1060–1071.
Evolution of reproductive–immune interactions.CrossRef | 1:CAS:528:DC%2BD28Xhtlent7rF&md5=cc2e39dacbd960c1798342acae4946e6CAS | 21672808PubMed | open url image1

Magnusson, W. E., and Taylor, J. A. (1982). Wallows of Crocodylus porosus as dry season refuges in swamps. Copeia 1982, 478–480.
Wallows of Crocodylus porosus as dry season refuges in swamps.CrossRef | open url image1

Markman, S., Muller, C. T., Pascoe, D., Dawson, A., and Buchanan, K. L. (2011). Pollutants affect development in nesting starlings Sturnus vulgaris. Journal of Applied Ecology 48, 391–397.
Pollutants affect development in nesting starlings Sturnus vulgaris.CrossRef | open url image1

Martin, L. B., Gilliam, J, Han, P, Lee, K, and Wikelski, M (2005). Corticosterone suppresses cutaneous immune function in temperate but not tropical House Sparrows, Passer domesticus. General and Comparative Endocrinology 140, 126–135.
| 1:CAS:528:DC%2BD2cXhtFahsrrE&md5=fb68afe52bc06b4cb4c10a9296314317CAS | open url image1

Martin, L. B., Han, P., Lewittes, J., Kuhlman, J. R., Klasing, K. C., and Wikelski, M. (2006). Phytohemagglutinin-induced skin swelling in birds: histological support for a classic immunoecological technique. Functional Ecology 20, 290–299.
Phytohemagglutinin-induced skin swelling in birds: histological support for a classic immunoecological technique.CrossRef | open url image1

Martin, L. B., Weil, Z. M., and Nelson, R. J. (2008). Seasonal changes in the vertebrate immune system: mediation by physiological trade-offs. Proceedings of the Royal Society of London. Series B, Biological Sciences 363, 321–339. open url image1

Matson, K. D., Cohen, A. A., Klasing, K. C., Ricklefs, R. E., and Scheuerlein, A. (2006). No simple answers for ecological immunology: relationships among immune indices break down at the species level in waterfowl. Proceedings of the Royal Society of London. Series B, Biological Sciences 273, 815–822.
No simple answers for ecological immunology: relationships among immune indices break down at the species level in waterfowl.CrossRef | open url image1

McCallum, M. L., and Trauth, S. (2007). Physiological trade-offs between immunity and reproduction in the northern cricket frog (Acris crepitans). Herpetologica 63, 269–274.
Physiological trade-offs between immunity and reproduction in the northern cricket frog (Acris crepitans).CrossRef | open url image1

Milnes, M. R., and Guillette, L. J. (2008). Alligator tales: new lessons about environmental contaminants from a sentinel species. Bioscience 58, 1027–1036.
Alligator tales: new lessons about environmental contaminants from a sentinel species.CrossRef | open url image1

Morgan, D. A., Ruscetti, F. W., and Gallo, R. (1976). Selective in vitro growth of T lymphocytes from normal human bone marrows. Science 193, 1007–1008.
Selective in vitro growth of T lymphocytes from normal human bone marrows.CrossRef | 1:STN:280:DyaE283ks1ahtg%3D%3D&md5=d3e3e36b0f93cb1ee1b1eadd7dcad4a6CAS | 181845PubMed | open url image1

Muller, W., Groothuis, T. G. G., Kasprzik, A., Dijkstra, C., Alatalo, R. V., and Siitari, H. (2005). Prenatal androgen exposure modulates cellular and humoral immune function of black-headed gull chicks. Proceedings of the Royal Society of London. Series B, Biological Sciences 272, 1971–1977.
Prenatal androgen exposure modulates cellular and humoral immune function of black-headed gull chicks.CrossRef | open url image1

Norris, K., and Evans, M. R. (2000). Ecological immunology: life history trade-offs and immune defense in birds. Behavioral Ecology 11, 19–26.
Ecological immunology: life history trade-offs and immune defense in birds.CrossRef | open url image1

Nowell, P. C. (1960). Phytohemagglutinin: an iniator of mitosis in cultures of normal human leukocytes. Cancer Research 20, 462–466.
| 1:CAS:528:DyaF3MXhvV2ruw%3D%3D&md5=307ffca9660c884037937b98e1b8ebccCAS | 14427849PubMed | open url image1

Rooney, A. A., Crain, D. A., Woodward, A. R., and Guillette, L. J. (2004). Seasonal variation in plasma sex steroid concentrations in juvenile American alligators. General and Comparative Endocrinology 135, 25–34.
Seasonal variation in plasma sex steroid concentrations in juvenile American alligators.CrossRef | 1:CAS:528:DC%2BD3sXpsVShurk%3D&md5=242128f707b2d7d91f2356fe0785275fCAS | 14644641PubMed | open url image1

Ruiz, M., French, S. S., Demas, G. E., and Martins, E. P. (2010). Food supplementation and testosterone interact to influence reproductive behavior and immune function in Sceloporus graciosus. Hormones and Behavior 57, 134–139.
Food supplementation and testosterone interact to influence reproductive behavior and immune function in Sceloporus graciosus.CrossRef | 1:CAS:528:DC%2BC3cXhtlantLc%3D&md5=27c3cf065020aca5f09f695b2a18844cCAS | 19800885PubMed | open url image1

Sarv, T., and Horak, P. (2009). Phytohaemagglutinin injection has a long-lasting effect on immune cells. Journal of Avian Biology 40, 569–571.
Phytohaemagglutinin injection has a long-lasting effect on immune cells.CrossRef | open url image1

Schwanz, L., Warner, D. A., McGaugh, S., Di Terlizzi, R., and Bronikowski, A. (2011). State-dependent physiological maintenance in a long-lived ectotherm, the painted turtle (Chrysemys picta). The Journal of Experimental Biology 214, 88–97.
State-dependent physiological maintenance in a long-lived ectotherm, the painted turtle (Chrysemys picta).CrossRef | 21147972PubMed | open url image1

Segner, H., Sundh, H., Buchmann, K., Douxfils, J., Sundell, K. S., Mathieu, C., Ruane, N., Jutfelt, F., Toften, H., and Vaughan, L. (2012). Health of farmed fish: its relation to fish welfare and its utility as welfare indicator. Fish Physiology and Biochemistry 38, 85–105.
Health of farmed fish: its relation to fish welfare and its utility as welfare indicator.CrossRef | 1:CAS:528:DC%2BC38XitFant7k%3D&md5=461775b3723a55348c9b51cf63a8dac8CAS | 21681416PubMed | open url image1

Shini, S., Kaiser, P., Shini, A., and Bryden, W. L. (2008). Biological response of chickens (Gallus gallus domesticus) induced by corticosterone and a bacterial endotoxin. Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology 149, 324–333. open url image1

Smits, J. E., and Williams, T. D. (1999). Validation of immunotoxicology techniques in passerine chicks exposed to Oil Sands tailings water. Ecotoxicology and Environmental Safety 44, 105–112.
Validation of immunotoxicology techniques in passerine chicks exposed to Oil Sands tailings water.CrossRef | 1:CAS:528:DyaK1MXmtFOks7s%3D&md5=d59083fdf393146bdaa195e52917e7e3CAS | 10499996PubMed | open url image1

Smits, J. E., Bortolotti, G. R., and Tella, J. L. (1999). Simplifying the phytohemagglutinin skin test technique in studies of avian immunocompetence. Functional Ecology 13, 567–572.
Simplifying the phytohemagglutinin skin test technique in studies of avian immunocompetence.CrossRef | open url image1

Tella, J. L., Lemus, J. A., Carrette, M., and Blanco, G. (2008). The PHA test reflects acquired T-cell mediated immunocompetence in birds. PLoS ONE 3, e3295.
The PHA test reflects acquired T-cell mediated immunocompetence in birds.CrossRef | 18820730PubMed | open url image1

Tschirren, B., Bischoff, L. L., Saladin, V., and Richner, H. (2007). Host condition and host immunity affect parasite fitness in a bird–ectoparasite system. Functional Ecology 21, 372–378.
Host condition and host immunity affect parasite fitness in a bird–ectoparasite system.CrossRef | open url image1

Turmelle, A. S., Ellison, J. A., Mendonca, M. T., and McCracken, G. F. (2010). Histological assessment of cellular immune response to the phytohemagglutinin skin test in Brazilian free-tailed bats (Tadarida brasiliensis). Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology 180, 1155–1164.
Histological assessment of cellular immune response to the phytohemagglutinin skin test in Brazilian free-tailed bats (Tadarida brasiliensis).CrossRef | 1:CAS:528:DC%2BC3cXht12qu7bM&md5=7f0fe92934fa283196c75699378589c6CAS | 20549214PubMed | open url image1

Turton, J. A., Ladds, P. W., Manolis, S. C., and Webb, G. J. (1997). Relationship of blood corticosterone, immunoglobulin and haematological values in young crocodiles (Crocodylus porosus) to water temperature, clutch of origin and body weight. Australian Veterinary Journal 75, 114–119.
Relationship of blood corticosterone, immunoglobulin and haematological values in young crocodiles (Crocodylus porosus) to water temperature, clutch of origin and body weight.CrossRef | 1:CAS:528:DyaK2sXhvVSgsLg%3D&md5=2b4ef5ab2b33a1dad6e61aa5ea9f8471CAS | 9066968PubMed | open url image1

Venesky, M. D., Wilcoxen, T. E., Rensel, M. A., Rollins-Smith, L., Kerby, J. L., and Parris, M. J. (2012). Dietary protein restriction impairs growth, immunity, and disease resistance in southern leopard frog tadpoles. Oecologia 169, 23–31.
Dietary protein restriction impairs growth, immunity, and disease resistance in southern leopard frog tadpoles.CrossRef | 22038058PubMed | open url image1

Vinkler, M., and Albrecht, T. (2011). Handling ‘immunocompetence’ in ecological studies: do we operate with confused terms? Journal of Avian Biology 42, 490–493.
Handling ‘immunocompetence’ in ecological studies: do we operate with confused terms?CrossRef | open url image1

Vinkler, M., Bainova, H., and Albrecht, T. (2010). Functional analysis of the skin-swelling response to phytohemagglutinin. Functional Ecology 24, 1081–1086.
Functional analysis of the skin-swelling response to phytohemagglutinin.CrossRef | open url image1

Vinkler, M., Schnitzer, J., Munclinger, P., and Albrecht, T. (2012). Phytohaemagglutinin skin-swelling test in scarlet rosefinch males: low quality males respond more strongly. Animal Behaviour 83, 17–23.
Phytohaemagglutinin skin-swelling test in scarlet rosefinch males: low quality males respond more strongly.CrossRef | open url image1

Webb, G. J. W., and Messel, H. (1978). Morphometric analysis of Crocodylus porosus from the north coast of Arnhem Land, northern Australia. Australian Journal of Zoology 26, 1–27.
Morphometric analysis of Crocodylus porosus from the north coast of Arnhem Land, northern Australia.CrossRef | open url image1

Youssef, S. A. H., El-Sanousi, A. A., Afifi, N. A., and El-Brawy, A. M. A. (1996). Effect of subclinical lead toxicity on the immune response of chickens to Newcastle disease virus vaccine. Research in Veterinary Science 60, 13–16.
Effect of subclinical lead toxicity on the immune response of chickens to Newcastle disease virus vaccine.CrossRef | 1:CAS:528:DyaK28Xht12hu7k%3D&md5=28e70e9a1c1f8f400ba83d5b029bda50CAS | open url image1

Zapata, A. G., Varas, A., and Torroba, M. (1992). Seasonal variations in the immune system of lower vertebrates. Immunology Today 13, 142–147.
Seasonal variations in the immune system of lower vertebrates.CrossRef | 1:CAS:528:DyaK38XkvVyjuro%3D&md5=199986f1bc3ebb583abc0e0587a0c39eCAS | 1580995PubMed | open url image1

Zayas, M. A., Rodriguez, H. A., Galoppo, G. H., Stoker, C., Durando, M., Luque, E. H., and Munoz-de-Toro, M. (2011). Hematology and blood biochemistry of young health broad-snouted caimans (Caiman latirostris). Journal of Herpetology 45, 516–524.
Hematology and blood biochemistry of young health broad-snouted caimans (Caiman latirostris).CrossRef | open url image1

Zimmerman, L. M., Paitz, R. T., Vogel, L. A., and Bowden, R. M. (2010). Variation in the seasonal patterns of innate and adaptive immunity in the red-eared slider (Trachemys scripta). The Journal of Experimental Biology 213, 1477–1483.
Variation in the seasonal patterns of innate and adaptive immunity in the red-eared slider (Trachemys scripta).CrossRef | 1:CAS:528:DC%2BC3cXot1Gnuro%3D&md5=505a4cc4bb046689b414f7c14c4f7f3aCAS | 20400632PubMed | open url image1

Zuk, M., and Johnsen, T. S. (1998). Seasonal changes in the relationship between ornamentation and immune response in red jungle fowl. Proceedings of the Royal Society of London. Series B, Biological Sciences 265, 1631–1635.
Seasonal changes in the relationship between ornamentation and immune response in red jungle fowl.CrossRef | open url image1

Zuk, M., and Stoehr, A. M. (2002). Immune defense and host life history. American Naturalist 160, S9–S22.
Immune defense and host life history.CrossRef | 18707455PubMed | open url image1



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