lmmunophenotypic characterization of primary and secondary lymphoid follicles

Thc need for an immunophenotypical referential framework relative to lymphoid follicle has led us to apply a panel of monoclonal and polyclonal antibodics, by means of a sensitive immunostaining method. Lymphoid follicle is an immunophenotypically complex structure made up of three lymphoid populations (B, being its bulk, and a few T and NK cells). dcndritic reticulum cells (DRCs) and Flemming's macrophagcs. Follicular B population is To 15 +. B1 + , OKB 7 +, HLA-DR + and C3bR +. In secondary follicles therc are differential characteristic reactivities for cach topographic compartment: Mantle zone is positive for OKB 2 and surface IgM (sIgM) and IgD (sIgD): germinal center (GC) clear zone (with centrocytic predominance) for OKT 9, sIgM and weakly for OKB 2: and GC dark zone (with centroblastic predoiniiiance) only for OKT 9. In sections, OKT 10 allows one to see immunoblasts and plasma cells, the latter being with lymphoplasmacytoid cells the only intracytoplasmic immunoglobulin holders. 10% of GC lympliocytcs are T cells, almost exclusively T-helper (Leu 3a +). Another 10% to 15% of lymphoid cells are Leu 7 (HNK- 1) +. In histological sections, DRCs are spccifically marked with R4123 and Flemming's inacrophages with anti-alpha,-antitrypsin and antialpha,- antichymotrypsin antibodies, both populations bcing negative to OKM 1 and OKM 5.