Expression of IgD on B cell malignancy. An immunopathological study of 50 cases

Expression of IgD was studied immunopathologically on 50 cases of B cell lymphomas (B MLs), together with various B cell markers including IgM, kappa and lambda chains, B1, B2, (OK)B2, (OB)B7, (OK)T10, NUB1, Leu 1, Leu 14, and PCA. IgD was demonstrated on 19 cases heavily and on 8 weakly. It associated well with expression of two antigens, B2 (C3d receptor molecule) and Leu1 (pan-T antigen), besides IgM, while, B2 was closely related in expression on B MLs to (OK)B2, (OK)B7, and NUB1. lambda chain was dominant on IgD heavily-stained cases. Histopathologically, IgD positive MLs were distributed in various types. All of diffuse intermediate type were shown to be IgD positive (4/4, 3 heavily). As cases of this type were shown to express most of other B cell antigens present on non-tumorous primary follicle B cells or mantle zone B cells, this type of MLs is speculated to be a neoplastic counterpart of such non-tumorous B cells. Eight out of 18 cases of diffuse large cell type were IgD heavily positive, suggesting some unusual mechanisms in IgD expression on these neoplastic large cells, as non-tumorous B cells lose most of their surface IgD soon after blastoid transformation. Other types of MLs were discussed with special emphasis on expression of IgD.