A human thymocyte antigen defined by a hybrid myeloma monoclonal antibody

Abstract

Spleen cells from a BALB/c mouse that had been immunized with human thymocytes were fused with the myeloma line P3‐NS1/1Ag 4.1. One of the resulting hybrid clones (NA1/34) secreted an antibody that was highly specific for human thymocytes. Eighty‐five % of thymocytes expressed the antigen designated HTA1. There were an estimated 15 × 10⁴ molecules of HTA1 per cell, and it is therefore a major surface molecule. The expression of this antigen on thymocytes appears to be reciprocal to HLA, as recognized by another monoclonal antibody W6/32. Immunoprecipitated material from [¹²⁵I]‐labeled thymocyte membranes was analyzed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate which disclosed a single component of 45 000 molecular weight.