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The clinical features of our cases demonstrated some of the already known characteristics of the variable spectrum of HIV infection. DA are the most important risk category in Italy. 10% of the ARC cases evolved into AIDS during a 12-month follow-up, on average. The most frequent OI in our AIDS cases were PCP, C. albicans esophagitis and chronic mucocutaneous ulcers. An high percentage of neurologic involvement from HIV was observed, and malignancies were encountered in AIDS (3 KS and 1 undifferentiated B lymphoma) as well as in ARC (1 Hodgkin's lymphoma). Statistically, significant worsening of the immunologic situation is evident as the disease progresses from LAS to AIDS. Activated B lymphocytes represent most of the cells of the germinal center during the hyperplastic stage of lymphadenopathy. Reversal of the T4/T8 ratio appears early during the initial stage of lymphadenopathy and is due to a decrease of CD4 and a relative increase of CD8. Also, destruction of the follicular dendritic cells is an early feature which becomes more evident as the disease advances and the lymph node evolves toward progressive involution. Activated B-lymphocyte augmentation with polyclonal Ig secretion appears to be related to T-independent B stimulation by coinfection such as CMV, EBV and HBV. The increase of cytotoxic/suppressor lymphocytes seems to be partly related to the excessive activation of B lymphocytes and partially directed to the cells infected by HIV or coated with its proteins (6,7,8,9). The destruction of follicular dendritic cells has been interpreted not only as a killer effect of the virus but also as a result of the intervention of CTL sensitized to the cells containing the virus (10,11). Their destruction may contribute to the impaired recognition of soluble antigen which is one of the main features of the immune deficiency of HIV infection (9,13,16).

The morphological and immunohistochemical findings in lymph nodes of nine patients with the acquired immunodeficiency syndrome (AIDS) and 81 patients with the AIDS-related complex (ARC) are presented. Three basic histological patterns were observed: follicular hyperplasia (29 cases), mixed hyperplasia (49 cases) and lymphocyte depletion (12 cases). While the first two variants were detected in typical ARC patients, lymphocyte depletion was always associated with AIDS. Immunohistochemistry on frozen sections showed that the number of B-cells varied throughout the series, being higher in the follicular type and significantly lower in the lymphocyte depletion nodes. The content of T-lymphocytes of the helper/inducer (T4) phenotype was reduced in all instances; this reduction was more pronounced in the germinal centres in follicular hyperplasia, while it involved all compartments of the node in the mixed and lymphocyte depletion types. In contrast the cytotoxic/suppressor (T8) subset was increased in the follicular and mixed hyperplasias only. Partial disintegration of the dendritic network in at least some of the follicles could be demonstrated in all lymph nodes. In the follicular and mixed hyperplasias there was a high number of proliferating B-cells in the germinal centres. Our data indicate the usefulness of grading the changes occurring in lymph nodes of patients with ARC and AIDS, and allow speculation as to the pathophysiology of these conditions.