Two distinct class II molecules encoded by the genes within the HLA-DR subregion of HLA-Dw2 and Dw12 can act as stimulating and restriction molecules

By using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), we investigated the difference in the HLA class II molecule between HLA-Dw2 and Dw12, both of which are typed as HLA-DR2 serologically. The anti-HLA-DR framework monoclonal antibody (MoAb) HU-4 precipitated an α-chain and two β-chains of human class II molecules from both Dw2 and Dw12 homozygous B lymphoblastoid cell lines. It was demonstrated clearly that an α-chain (α¹) and one of the β-chains (β¹) showed no difference in mobility in the 2D-PAGE between Dw2 and Dw12, but that another β chain (β²) of Dw2 was distinct from that of Dw12 in the 2D-PAGE profile. Thus, MoAb HU-4 precipitated α¹β¹ and α¹β² molecules from Dw2 and Dw12, and the α¹β¹ molecule appears to be an HLA-DR2 molecule. The α¹β² molecule, on the other hand, is a class II molecule distinct from those precipitated with anti-DR2, anti-DQw1 (DC1, MB1, MT1), or anti-FA MoAbs. MoAb Hu-4 completely inhibited the mixed lymphocyte culture reaction (MLR) between Dw2 and Dw12, but anti-DR2 MoAb HU-30, which reacts only with the α¹β¹ molecule, did not show an inhibitory effect on the MLR between DW2 and Dw12. The α¹β² molecule is therefore the molecule which elicits MLR between Dw2 and Dw12. An IL 2-dependent T cell line established from an HLA-Dw12/D blank heterozygous high responder to the streptococcal cell wall antigen (SCW) clearly distinguished the Dw2 specificity from Dw12 specificity expressed on the antigen-presenting cell (APC). Moreover, MoAb HU-4 markedly inhibited the cooperation between the T cell line and APC to respond to SCW. These observations indicate that the α¹β² is recognized as a restriction molecule by the T cell line at the antigen presentation of SCW through APC. MoAb HU-30 on the other hand partially inhibited the MLR between Dw2 or Dw12 homozygous cell as a stimulator cell and non DR2 cell as a responder cell. It markedly inhibited the proliferative response of the DW12/D^- heterozygous T cell line to SCW, presented by Dw2⁺ but Dw12^- allogeneic APC, and the peripheral response of Dw2 or Dw12 homozygous peripheral blood lymphocytes to SCW. Thus, two distinct class II molecules encoded by the genes within the HLA-DR subregion of HLA-Dw2 and Dw12 can act as stimulating molecules in the MLR and as restriction molecules in the antigen presentation by APC.