A novel cell surface proliferation-associated marker expressed on T cells and up-regulated on germinal center B cells

In this study we present data on a novel cell surface antigen recognized by monoclonal antibody (mAb) VPM30, originally thought to recognize only bovine and ovine sIg(+) B cells from peripheral blood. Here we show that the antigen, molecular mass 28 kDa, is not only found in B cell follicles in frozen sections, but when used on paraffin sections VPM30 specifically stains B cells in the Light zone of germinal centers but not in the mantle or dark zones. In addition we show that the antigen is also expressed by 90% of T cells after activation, with kinetics of antigen expression mirroring those of proliferation. By both size and distribution, the antigen appears to be novel, corresponding to no known cluster of differentiation, and will be of great use in the study of ruminant cellular immune responses.