A DR7 SPECIFIC MONOCLONAL ANTIBODY TAL13.1, RAISED AGAINST A TRANSFECTANT DETECTS IL‐4 UPREGULATED ANTIGEN ON PERIPHERAL B‐LYMPHOCYTES

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Abstract
A monoclonal antibody TAL13.1 was raised against mouse L cells transfected with the human HLA‐DRB 1*0701 gene. This antibody was found to be polymorphic recognizing a determinant expressed by the DR7, DRβ1*0701 and DRB1*0702 gene products. Four polymorphic sites unique to this specificity have been identified within the DR pi domain. These are residues 11–14, 25, 30 and 71–74, one or a combination of which is postulated as being responsible for conferring the specificity of the antibody. In Western blot analysis TALI3.1 was found to react with the DRαβ dimer, but not with the free α or β chains. However, in flow cytometry it failed to bind a DRα/DQβ mixed pair transfectant confirming that it recognizes an epitope on the DRβ not the DRα chain. Although TAL13.1, a low affinity antibody is negative or only weakly positive on resting peripheral blood lymphocytes (PBLs), we have demonstrated that by interleukin‐4 (IL‐4) stimulation we can up‐regulate the levels of antigen already present and gain a level of binding comparable to that found on B lymphoid cell lines (B‐LCLs) where it has been found to be a valuable reagent in their characterization.