Immunohistochemical identification of immune cell subsets in formalin- and zinc-fixed, paraffin-embedded tissues from chicken and duck using commercial antibodies.

Immunohistochemical identification of immune cells in poultry has primarily been performed using frozen tissues, with limited identification in paraffin-embedded tissues. In this study, the following 18 commercially available primary antibodies associated with immune cell phenotypes were tested: anti-CD3, CD4 (clone CT-4 and 2-35), TCRγδ, TCRαVβ1, TCRαVβ2, CD8, BAFF-R, PAX5, Bu-1a/b, Iba-1, MRC1L-B, CSF-1R, TIM4, MHC class II (clone 2D5 and 21-1A6), MUM1, and CD45 antibodies in formalin-fixed, paraffin-embedded (FFPE) and zinc-fixed, paraffin-embedded (ZFPE) chicken and duck lymphoid tissues. In chickens, 11 antibodies in FFPE tissue and 16 in ZFPE tissue reacted with the expected antigens under some of the antigen retrieval conditions tested. Antibodies against CD4 (clone CT-4), TCRγδ, TCRαVβ1, CSF-1R, and MHC class II (clone 21-1A6) were effective only in ZFPE tissue. In ducks, cells in both FFPE and ZFPE tissues were immunolabeled by five antibodies under some of the conditions tested. Antigen retrieval suitable for cellular membrane antigen tended to be heat for FFPE tissues and no treatment for ZFPE tissues. Heat-induced antigen retrieval allowed for better detection of nuclear antigens in both FFPE and ZFPE sections. Our results indicate that commercially available antibodies can immunohistochemically detect some of chicken and duck immune cell subsets in paraffin-embedded sections.