Cross-reactive anti-chicken CD4 and CD8 monoclonal antibodies suggest polymorphism of the turkey CD8 alpha molecule

To measure turkey CD4 and CD8 T cell levels, the cross-reactivity of mouse anti-chicken CD4 and CD8 monoclonal antibodies (mAb) with turkey leucocytes was tested by flow cytometric analysis of blood obtained from individuals in five turkey lines. The turkey lines used included a randombred control p opulation (RBC2), a subline (F) of RBC2 selected for increased 16-wk BW, an d a sire line (A, B, and C)from each of three commercial turkey breeders. P eripheral blood lymphocytes were isolated and stained with single or dual c olor staining. The CT8 mAb (anti-chicken CD8 alpha) failed to detect the CD 8 alpha molecule in some turkeys, and there were large line differences in ability to detect the CD8 alpha molecule. However, certain anti-chicken CD8 alpha mAb (3-298, 3-292 and 11-39) had good cross-reactivity with the turk ey CD8 alpha molecule. These present data indicate that the turkey CD8 alph a: molecule is polymorphic. Some anti-chicken CD4 mAb (CT4, 2-6, 2-35, and 7-125) were also crossreactive with the turkey CD4 molecule. Immunoprecipit ation and Western blotting showed that the 3-298 mAb precipitated a 33- to 35-kDa polypeptide from the turkey splenocyte lysate under reducing conditi ons. The availability of cross-reactive anti-chicken CD4 and CD8 mAb will f acilitate the studies of immune responses in turkeys.