Specific anti-hairy cell and anti-B cell antisera: characterization of surface antigens and origin of hairy cells.

Hairy cells obtained from nine patients with hairy cell leukaemia were found to be sensitive to a heterologous anti-human B lymphocyte serum using a cytotoxicity assay and the ultrastructural characterization after immunoperoxydase labelling. This antiserum raised in the rabbit and rendered specific by extensive absorptions with human immunoglobulins, erythrocytes, thymocytes and monocytes, reacted with normal and pathological B lymphocytes but not with monocytes, as demonstrated by ultrastructural studies. In addition, a heterologous anti-hairy cell serum was prepared and absorbed with erythrocytes, thymocytes and monocytes. The in vitro properties of this antiserum were identical to those of the anti-human B cell serum in the various assays: cytotoxicity, rosette inhibition and ultrastructural characterization. These results demonstrate that hairy cells of the studied patients express surface antigenic specificities of the B cell population, not shared by monocytes. Further absorption of the anti-hairy cell serum with CLL cells suggested that hairy cells express other characteristic antigens in addition to the B lymphocyte antigens. HLA-DR alloantigens were also shown to be present at the surface of hairy cells. This type of immunological analysis may prove to be of help in the understanding of the differentiation abnormalities in the hairy cell leukaemia as well as in other lymphoproliferative disorders.