Transcription of the unique ruminant class II major histocompatibility complex-DYA and DIB genes in dendritic cells

Dendritic cells (DG) constitute the most effective immune cell population f or priming and recalling T cell responses to foreign antigens. DC patrol th e peripheral tissues collecting foreign antigen for subsequent presentation by classical class II MHC molecules to T cells in the draining lymph nodes . Since the description of the DYA and DIB class II MHC genes, which are un ique to ruminants, no transcript or protein have been reported. Here we pro vide evidence that these genes are transcribed in cattle and that paired tr anscription is restricted in afferent lymph to a functionally distinct popu lation of DC. Analysis of lymph node, lung and thymus suggests that tissue DC also transcribe both genes. Cytokine-induced differentiation of cultured monocytes to a DC phenotype is linked with induction of both DYA and DIB t ranscription. This is consistent with an association of their products with the potent antigen presenting capacity of these cells in cattle.