RETICULAR CRYPT EPITHELIUM AND INTRAEPITHELIAL LYMPHOID-CELLS IN THE HYPERPLASTIC HUMAN PALATINE TONSIL - AN IMMUNOHISTOCHEMICAL ANALYSIS

Extensive immunohistochemical analyses of the hyperplastic human palat ine tonsil disclosed variegated B cell phenotypes on the lymphoid cell s among the crypt epithelium. The reticular epithelial network was evi dent by cytokeratin immunostaining. The reticular epithelium near the crypt lumen was positive for lysozyme. Secretory component was negativ e, while HLA-DR was frequently expressed. Intramucosal small lymphocyt es, densely distributed in the luminal side, consisted mainly of B cel ls expressing CD19, CD20, CD21, CD22, CD45R, CD74, DBB42, HLA-DR, HLA- DQ, bcl-2 protein and surface IgM. Some B cells revealed mantle zone p henotypes (surface IgD(+), CD5(+), CD24(+), DBA44(+), CD10(-), DNA7(-) ). Cells of germinocyte phenotype (CD10(+), DNA7(+)) were sparsely see n. A good number of intramucosal lymphoid cells were further labeled f or CD11b, a phenotype of so-called B-1 cells. Plasma cells were cluste red within the basal half. IgG was their major immunoglobulin class, f ollowed by IgA, IgM and IgD classes. A smaller number of T cells (CD2( +), CD3(+), CD5(+), CD45RO(+), TCR alpha beta(+)) were identified amon g the epithelium. CD4(+) cells predominated over CD8(+) cells. TCR gam ma delta(+) cells were rare. Macrophages (CD68(+)), dendritic histiocy tes (S-100 protein(+), CD1(+)), and natural killer cells (CD16(+) or C D57(+)) were also dispersed. Another unique feature of this lymphoepit helial complex was the existence of HLA-DR-intramucosal microvasculatu re, where lymphocyte recirculation was suggested. Proliferating cell n uclear antigen was detected commonly in the epithelial cells but rarel y in the lymphoid cells. Possible lymphoepithelial interactions and mo rphologic similarities to the thymic medulla are discussed.