Clonal T cell responses reflect the expression of multiple DQ genes in cattle.

Cattle express Major Histocompatibility Complex (MHC) class I1 products encoded by the DR and DQ loci. Each haplotype expresses a single DR product, and one or more DQ products due to duplication of the DQ locus in about half the common cattle haplotypes. In order to define the roles of the individual class I1 products in antigen presentation and T cell responses, we are cloning and transfecting the class I1 genes expressed by a pair of immunologically-characterised animals. These animals 10795: class I1 haplotypes DHIA, DH24A; 10814 : DHlSB, DH24A share one MHC haplotype, and exhibit distinct responses to immunisation with a peptide antigen derived from Foot-andMouth Disease virus (FMDV15)[1,2].