Phenotypic changes on hairy cells exposed in vitro to interferons: a quantitative FACS study

In vitro culture of hairy cells (HC) (five patients) with alpha IFN (100 U/ml) significantly enhanced MHC and CD22 antigen expression and reduced CD25, sIg and FMC7 positivity, together with consistent but not significant reductions in CD9, 19 and HC2. A sixth patient, who was refractory to the effects of alpha IFN in vivo, was also studied and none of these changes were seen in her HC when cultured with alpha IFN in vitro. gamma IFN (100 U/ml) produced a much less marked increase in MHC and reduced sIg. TPA (100 ng/ml) induced changes very similar to those observed with alpha IFN. alpha and gamma IFN had no effect on a range of other antigens in HCL (including CD23 and 38, and transferrin receptors) and also produced no significant antigenic changes in CLL cells. It is concluded that these findings are compatible with partial activation/maturation of HC by alpha IFN. It is suggested that the specificity of the phenotypic changes induced on HC by alpha IFN is a consequence of HC representing a stage of B-cell development at which alpha IFN has specific immunomodulatory effects.