Human T-cell clones used to define functional epitopes on HLA class II molecules.

Polyclonal reagents have been used to define HLA class II molecules in conventional serologic and cellular typing. We generated human alloreactive T-cell clones to analyze the functional fine specificities of HLA class II molecules that might be important for the phenomenon of HLA and disease association. We chose to examine HLA-Dw14, an HLA-D specificity that has been associated with juvenile rheumatoid arthritis. In this paper we have presented data that suggest that conventional cellular typing does not reflect the distribution of T-cell epitopes on major histocompatibility complex class II molecules. We describe three alloreactive T-cell clones that have defined three separate Dw14-associated T-cell epitopes. Two of these epitopes were on a DR-region molecule; the third was located on a DQ-region product. In a panel of unrelated DR4-positive donors, these three DW14-associated determinants were present in a high frequency but were not linked to each other. Within the tested panel of DR4-positive cells, all possible combinatorial arrangements of these three allodeterminants were seen. The concurrent expression of any two of the three allodeterminants was equivalent to a positive typing response for Dw14. Our finding that HLA-Dw14 is not characterized by a unique allodeterminant but by the combinatorial recognition of independently distributed T-cell interaction sites suggests that analysis of HLA and disease association may be more clearly demonstrated through the use of human T-cell clones.