Yoder Lab: Research Interest

Natural Killer Receptors (NKRs) in Zebrafish

Species ranging from humans to fish, frogs and reptiles possess natural cytotoxic cells as part of the innate immune system that recognize and destroy “non-self” or foreign antigens. Mammalian natural killer (NK) cells utilize inhibitory and activating cell surface receptors to differentiate between “normal” cells and virally infected or transformed cells. In general, inhibitory (non-killing) NK receptors (NKRs) recognize MHCI as a marker of “self” which stimulates a signaling cascade leading to the inhibition of NK mediated target lysis. In contrast, certain activating (killing) NKRs have been shown to recognize virally encoded or stress-related proteins and stimulate a signaling cascade leading to target cell destruction. Such activation of NK cells can also occur when endogenous MHCI is down regulated as in certain types of tumors. These signaling cascades within NK cells must be carefully balanced because defects in NK function can result in tumor progression or an autoimmune response, both presenting dangerous consequences to the individual. Although much is known about mammalian NKRs, only limited information is known about NKRs in non-mammalian model species.

Multi-gene families of mammalian NKRs are encoded by the leukocyte receptor complex (e.g. KIRs), the natural kilelr complex (e.g. Ly49s) and the CD94/NKG2 complex. NKRs can be further classified based on their extra-cellular domains: possessing either immunogobulin domains (KIRs) or C-type lectin domains (Ly49s and NKG2). Our laboratory is working on identifying and characterizing the functional orthologs of NKRs in bony fish, primarily using zebrafish as a model species.


Novel immune-type receptors (NITRs) were originally detected in a gene discovery experiment (in Gary Litman's laboratory) designed to identify novel genes related to T-cell receptor (TCR) genes from the compact genome of pufferfish. NITR genes have since been identified and characterized from multiple fish species, including the experimentally amenable zebrafish. As in TCR genes, all NITRs genes encode authentic variable (V) domains and some encode joining regions (J) but there is no evidence for recombination of the NITR genes; the V-J regions are germ-line joined in a single exon. This unique feature suggests that the NITRs may represent what was once the primordial gene(s) that gave rise to the adaptive immune receptors. We continue to collaborate with Gary Litman's Lab on the study of NITRs in zebrafish.


Immune-related, lectin like receptors (ILLRs) were identified in a zebrafish genome screen to identify multi-gene families of C-type lectin domain (CTLD) receptors that may function in natural cytotoxicity paralling the mammalian NKRs (Ly49 and CD94/NKG2). ILLRs are a multi-gene family of Group II CTLD receptors that possess the intracellular signaling capacity to function as NK receptors. ILLRs are differentially expressed in the zebrafish lymphoid and myeloid lineages suggesting diversified functions. We have shown that the candidate activating receptor Illr3 can initiate target cell killing within the context of human NK cells supporting a role for Illr3 in natural cytotoxicity.


Comparative studies in multiple primate and rodent species have shown that the NKR genes are recently and rapidly evolving. For example, the multigenic KIRs in human have been shown to play critical roles in NK cell function but are only present as two genes in mouse. Independently, mice have evolved to utilize the multigenic C-type lectin receptors (Ly49), that are structurally unrelated to KIRs, for NK function: humans possess a single Ly49 pseudogene. These observations suggest that studies of diversified NKRs from a variety of species including the zebrafish are directly relevant to understanding human NK cell function.

Although searches of the human and mouse genomes have not identified mammalian genetic orthologs to the NITR or ILLR genes, NITRs are very similar to the human KIRs in their protein architecture (with the exception of possessing a V domain) and ILLRs are similar to the mammalian Ly49 and NKG2 families of NKRs. Current data suggests that the NITRs and ILLRs may function as NKRs in bony fish.

Our research program transcends the boundaries of a single field of study in order to gain a broader and better understanding of innate immune function. The zebrafish offers a powerful tool for dissecting the genetics of disease susceptibility and resistance. Clearly the identification of genetic pathways that are conserved between zebrafish and human makes it a great model for human disease. However, what might be the most medically relevant will be what makes zebrafish immunity different from that of a human.

Related Publications:
Yoder, J.A. and G.W. Litman. 2011. The phylogenetic origins of natural killer receptors and recognition: relationships, possibilities and realities. Immunogenetics. 63:123-141. PMID: 21191578
f1000 Yoder, J.A., P.M. Turner, P.D. Wright, V. Wittamer, J.Y. Bertrand, D. Traver and G.W. Litman. 2010. Developmental and tissue-specific expression of NITRs. Immunogenetics. 62:117–122. PMID: 20012603
Yoder, J.A. 2009. Form, function and phylogenetics of NITRs in bony fish. Dev Comp Immunol. 33:135-44. PMID: 18840463
Desai, S., A.K. Heffelfinger, T.M. Orcutt, G.W. Litman and J.A. Yoder. 2008. The medaka novel immune-type receptor (NITR) gene clusters reveal an extraordinary degree of divergence in variable domains. BMC Evol. Biol. 8:177. PMID: 18565225
Yoder, J.A., J.P. Cannon, R.T. Litman, C. Murphy, J.L. Freeman and G.W. Litman. 2008.  Evidence for a transposition event in a second NITR gene cluster in zebrafish.  Immunogenet. 60: 257-265. PMID: 18330557
Wei, S., J. Zhou, X. Chen, R.N. Shah, P.K. Epling-Burnette, J. Liu, T. Orcutt, D. Traver, J.Y. Djeu, G.W. Litman and J.A. Yoder. 2007. The zebrafish activating immune receptor Nitr9 signals via Dap12. Immunogenet59: 813-821. PMID: 17891481
Litman, G.W., J.P. Cannon, L.J. Dishaw, R.N. Haire, D.D. Eason, J.A. Yoder, J. Hernandez Prada, D.A. Ostrov. 2007. Immunoglobulin variable regions in molecules exhibiting characteristics of innate and adaptive immune receptors. Immunol. Res. 38: 294-304. PMID: 17917037
Panagos, P.G., K.P. Dobrinski, X. Chen, A.W. Grant, D. Traver, J.Y. Djeu, S. Wei and J.A. Yoder. 2006.  Immune-related, lectin-like receptors are differentially expressed in the myeloid and lymphoid lineages of zebrafish.  Immunogenet. 58:31-40. PMID: 16467987
f1000 Yoder, J.A., R.T. Litman, M.G. Mueller, S. Desai, K.P. Dobrinski, J.S. Montgomery, M.P. Buzzeo, T. Ota, C.T. Amemiya, N.S. Trede, S. Wei, J.Y. Djeu, S. Humphray, K. Jekosch, J. Hernandez Prada, D.A. Ostrov, G.W. Litman. 2004. Resolution of the NITR gene cluster in zebrafish. Proc. Natl. Acad. Sci.  101: 15706-15711. PMID: 15496470
Litman, G.W., J.A. Yoder, J.P. Cannon and R.N. Haire. 2003. Novel immune-type receptor genes and the origins of adaptive and innate immune recognition. Integrative and Comparative Biology. 43: 331-337. PMID: 21680441
van den Berg, T.K., J.A. Yoder and G.W. Litman. 2003. On the origins of adaptive immunity: possible clues from the SIRP and NITR multigene families.  Trends Immunol. 25:11-16. PMID: 14698279
Yoder, J.A., M.G. Mueller, T. Ota, K. Nichols, S.S. Ristow, G.H. Thorgaard and G.W. Litman. 2002. Cloning novel immune-type inhibitory receptors from the rainbow trout, Oncorhynchus mykiss. Immunogenet54: 662-670. PMID: 12466899
Yoder, J.A., M.G. Mueller, C. Wei, B. Corliss, D.M. Prather, T. Willis, R.T. Litman, J. Djeu and G.W. Litman. 2001. Immune-type receptor genes in zebrafish share genetic and functional properties with genes encoded by the mammalian leukocyte receptor complex.  Proc. Natl. Acad. Sci. 98: 6771-6776. PMID: 11381126
Litman, G.W., N.A. Hawke and J.A. Yoder.  2001. Novel immune-type receptors.  Immunol. Rev181: 250-259. PMID: 11513146
Hawke, N.A., J.A. Yoder, R.N. Haire, M.G. Mueller, R.T. Litman, A.L. Miracle, T. Stuge, N. Miller and G.W. Litman. 2001. Extraordinary variation in a diversified family of immune-type receptor genes.  Proc. Natl. Acad. Sci. 98: 13832-13837. PMID: 11698645