Heterologous B‐Cell Antisera May Detect Non‐Ig, Non‐HLA‐DR Antigens

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Abstract
A heterologous antiserum (antiserum 7420) against B‐lymphocyte antigen(s) was raised in a rabbit by immunization with peripheral blood lymphocytes from a patient with chronic lymphocytic leukaemia (CLL). After absorptions with pooled normal human serum, IgA, IgD, and IgM M‐components, the fluorescein isothiocyanate‐conjugated F(ab′)2 fragments were prepared and further absorbed with normal peripheral blood leucocytes. The F(ab′)2 fragments, studied in direct immunofluorescence, reacted with both normal and CLL B lymphocytes but not with T lymphocytes. Comparative studies with an HLA‐DR antiserum showed that the antigen(s) detected by 7420 antiserum did not redistribute together with HLA‐DR antigens in cocapping experiments, nor did the HLA‐DR antiserum block the reaction of 7420 F(ab′)s fragments with B lymphocytes. The 7420 F(ab′)z fragments precipitated detergent‐solubilized B‐cell membrane material with a molecular weight of around 40,000 and 150,000 daltons. The conclusion drawn is that the 7420 and HLA‐DR antigens are different. The 7420 antigen was also shown to be different from classical HLA antigens, β2‐microglobulin, surface immunoglobulin, the Fc receptor, and HC protein.