Generation of large granular lymphocytes and lymphocyte subset changes linked with cyclophosphamide-induced eosinophilia in rats--and the effects of ciclosporin.

Administration of cyclophosphamide (Cy: 150 mg/kg i.p.) to rats 48 h before immunization with a T-dependent antigen (ovalbumin) resulted in a striking absolute eosinophilia in blood, bone marrow, and secondary lymphoid organs after 10 to 14 days. This eosinophilia was preceded by a significant increase in the W3/25+/OX-8+ (T helper/inducer to T cytotoxic/suppressor) ratio in lymph nodes and spleen and accompanied by a pronounced rise in splenic OX-12+ (B cell) numbers. There was also a concomitant increase in cells with the morphology and immunophenotype (OX-8+, OX-19-) of large granular lymphocytes (LGL). It is suggested that the eosinophilia linked with the B lymphocytosis may be due to cell-derived soluble factors, including a possible equivalent of eosinophil differentiation factor (EDF = interleukin 5), which also has B-cell growth factor activity (BCGF II) in mice. Ciclosporin (CsA; 25 mg/kg/day per os) from the time of immunization, did not affect the incidence of W3/25+ cells in spleen or lymph nodes, but abrogated Cy-induced eosinophilia and reduced the extent of B-cell proliferation. In addition, CsA caused a further, marked increase in the incidence of OX-8+, OX-19-LGL within the spleen. The functional role(s) of these latter cells remains to be defined.