Immunosurveillance, immunodeficiency and lymphoproliferations.

The incidence of malignant lymphomas is significantly higher in patients who have congenital or acquired immunodeficiencies. Although there are some differences between these immunodeficiency-associated lymphoproliferative disorders (IALD), they share several features: a tendency to present in extranodal sites, particularly the central nervous system and gastrointestinal tract, rapid clinical progression when untreated, diffuse large cell histology, B-cell origin and association with the Epstein-Barr virus (EBV). In the presence of disturbed T-cell function EBV may induce not only prolonged proliferation but also transformation of B-cells. In patients with primary, congenital immunodeficiency the incidence of IALD ranges from 0.7% for patients with X-linked agammaglobulinemia to 12-15% in patients with ataxia telangiectasia. In patients with post-transplant lymphoproliferative disorders (PT-LPD) the incidence varies from 0.5% after bone marrow transplantation to 10% after heart-lung transplantation. PT-LPD are often characterized by a polymorphic cell population. Recent studies identified three categories: plasmacytic hyperplasia, polymorphic lymphoproliferation and B-cell non-Hodgkin's lymphoma (NHL). The plasmacytic hyperplasias are of polyclonal composition, while polymorphic lymphoproliferations and NHL are monoclonal. The precise risk of lymphoma development in HIV infection is not defined, but estimates suggest a prevalence of 3-4%. HIV-related NHLs are divisible by site of manifestation into systemic, primary central nervous system and body-cavity lymphomas, and by pathology into Burkitt's and Burkitt's-like lymphoma, and diffuse large cell lymphoma (DLCL). In about 90% of cases these lymphomas are of monoclonal B-cell composition. Recent experiences suggest a link between therapy with immunosuppressive drugs (methotrexate, azathioprine, cyclophospamide, etc.) and development of IALD, best supported by the increased rate of IALD in patients with rheumatoid arthritis who receive methotrexate therapy. The occurrence of IALD demonstrates the importance of competent immunosurveillance in the development of lymphoid neoplasias, which may have therapeutic relevance too.