A NOVEL PERIPHERAL CD4(-CELL POPULATION - INHERITANCE OF CD8-ALPHA EXPRESSION ON CD4(+) T-CELLS()CD8(+) T)

In this study we show the inheritance of a CD4(+)CD8(+) peripheral T c ell population in the H.B15 chicken strain. A large proportion of alph a beta T cells in peripheral blood (20-40%), spleen (10-20%) and intes tinal epithelium (5-10%) co-express CD4 and CD8 alpha, but not CD8 bet a. CD4(+) CD8 alpha alpha cells are functionally normal T cells, since they proliferate in response to mitogens and signals delivered via th e alpha beta T cell receptor as well as via the CD28 co-receptor. Thes e cells induce in vivo a graft versus host-reaction, providing further evidence for their function as CD4(+) T cells. The CD4(+)CD8 alpha al pha T cell population was found in 75% of the first progeny and in 100 % of further progenies, demonstrating that co-expression of CD4 and CD 8 on peripheral T cells is an inherited phenomenon. In addition, cross -breeding data suggest a dominant Mendelian form of inheritance. The h ereditary expression of CD8 alpha on peripheral CD4(+) T cells in chic ken provides a unique model in which to study the regulation of CD4 an d CD8 expression.