IgA and IgM cytoplastic inclusions in a series of cases of chronic lymphocytic leukaemia.

Seventy-two cases of typical chronic lymphocytic leukaemia were screened by electron microscopy for the presence of intracytoplasmic immunoglobulin crystals. Immunoglobulin inclusions were found in four cases. Immunofluorescent studies showed that the inclusions contained IgA in two cases and IgM in the other two patients. Lambda light chain specificity was demonstrated in all four cases. The ultrastructure of the inclusions was identical in each patient except that in one of the IgA cases the inclusions were found in the perinuclear cistern in addition to the more usual location within cisternae of rough endoplasmic reticulum. Surface immunofluorescence showed mu heavy chains in the two cases displaying IgM crystal formation, but in the two IgA patients, no alpha heavy chains were demonstrable at the cell surface. The possible significance of these findings is discussed in relation to the existing literature.