Role of lymphoid organs in the pathogenesis of human immunodeficiency virus (HIV) infection

The pathogenic mechanisms of HIV disease are multifactorial and multi-phasic. The common denominator of the disease is the profound immunosuppression that occurs in the vast majority of infected patients. Studies in lymphoid tissues in HIV disease have provided considerable insight into the pathogenic processes involved from the earliest phases of infection through the advanced stages. Following primary infection, virus is disseminated throughout the body and seeds the lymphoid tissue where its replication is only incompletely suppressed and where a reservoir of virus is established. Extracellular virus is trapped within the FDC of the lymph node germinal centers and serves as a source of infection for cells which reside in or migrate through the lymph node throughout the course of infection even during the early and often prolonged asymptomatic period. Eventually, the architecture of the lymphoid tissue is destroyed, compounding the immune dysfunction that results from the depletion of CD4+ T cells. In this regard, the lymphoid tissue of LTNPs is relatively intact and viral burden and replication is considerably lower in the peripheral blood and lymph node mono-nuclear cells of LTNPs than in individuals whose disease progresses. Cytokines probably play a major role in the modulation of HIV expression in the milieu of the lymphoid tissue. Further understanding of the pathogenic mechanisms operative in the lymphoid tissues of HIV-infected individuals will have important implications in the design of therapeutic strategies involving both antiretroviral and immunomodulatory approaches.