PTPRK and Immunodeficiency: Intriguingly, rescue experiments in the aforementioned mutant rats underscored that the RPTPκ and Themis proteins jointly contribute to the immunodeficiency phenotype (Iwata et al., 2010), providing a real conundrum as to what the net effects are of the many variants that reside in intronic regions and the intergenic sequence in the PTPRK/THEMIS locus.