Enzyme and immunohistochemistry of follicular hyperplasia in AIDS-related lymphadenopathy.

We used a panel of monoclonal and polyclonal antibodies to analyze frozen and paraffin-embedded lymph node biopsy specimens from 25 intravenous drug abusers (IVDA) with acquired immunodeficiency syndrome (AIDS)-related lymphadenopathy histologically characterized by follicular hyperplasia. Our aim was to obtain diagnostic clues to this commonly occurring pattern. Double-labelling immunohistological studies were also performed on selected frozen sections and 13 plastic-embedded specimens were tested by a number of enzyme reactions. Consistent features in IVDA included abnormally high numbers of intrafollicular T-cells, positive for acid phosphatase and beta-glucuronidase, most of which had Leu-2a-positive phenotype; a marked reduction or loss of mantle zone B-cells (positive for surface IgD-IgM and alkaline phosphatase); and disarray of the network of follicular dendritic reticulum cells (DRCs), as revealed with DRC-1 and anti-S-100 protein antibodies or with reaction for 5'-nucleotidase. When present, distinctive intrafollicular clusters of Leu-2a-positive T-cells and mantle zone B-cells were nearly always associated with areas lacking DRCs in some patients. The intrafollicular hypervascularity invariably found in IVDA proved to be of a true capillary nature, as demonstrated by alkaline phosphatase, 5'-nucleotidase, and ATPase reactions. In control tissues, all showing absence of Leu-2a-positive intrafollicular T-cells, most of the above individual changes could be detected, although they were occasional, mild, and never associated within the same follicle. By contrast, combined immunohistological and enzyme histochemical findings in IVDA indicated that in most follicles such changes were marked and very often associated within the same follicle in each case.(ABSTRACT TRUNCATED AT 250 WORDS)