Absence of a receptor for fixed C3 on the hairy cells of leukaemic reticuloendotheliosis.

By the use of a rosette test employing yeast particles coated with C3 activated by the alternative pathway, we have demonstrated that the hairy cells of leukaemic reticuloendotheliosis (LRE) do not possess a receptor for C3. It is also shown that hairy cells display a consistently lower percentage of rosette formation with ox EAC than with ox EA IgM and this is attributed to varying degrees of steric hindrance of IgM or incomplete coating by complement. Blocking with monomeric IgM confirmed this interpretation. These results are used to reconcile previously conflicting reports concerning the presence or absence of a receptor for C3 on the hairy cells of LRE, and to suggest that the disease is accompanied by a severe reduction of normal B lymphocytes.