Differential effects of anti‐CD45 monoclonal antibody on human B cell proliferation: a monoclonal antibody recognizing a neuraminidase‐sensitive epitope of the T200 molecule enhances anti‐immunoglobulin‐induced proliferation

We have generated seven monoclonal antibodies (mAb) that recognize the T200 molecule. These mAb have been classified by competitive binding assay in flow cytometry into three groups each reacting with a different epitope of the T200 molecule: (a) 136-4B5, that shows a sialic acid nature, (b) 135-4H9, 135-4C5, 144-2, 155-2 and (c) 72-5D3, 124-2H12b. A heterogeneous effect was observed when they were tested on an anti-immunoglobulin-induced B cell proliferation. Whereas 72-5D3 and 135-4H9 mAb inhibited the proliferative response of B cells, 136-4B5 mAb greatly enhanced it, both effects being dose dependent. We can conclude that anti-CD45 mAb have a different and contrary functional behavior on anti-Ig-induced B cell proliferation, depending on the epitope recognized. The basis for such a difference could reside in the glucidic nature of the epitope recognized by the 136-4B5 mAb.