THE ACQUIRED IMMUNODE~~CIENCY SYNDROME (AIDS) was described at the beginning of the last decade with the observation of opportunistic infections (especially Pneumocystis pneumonia) and Kaposi’s sarcoma within homosexual men with marked acquired immunosuppression [ 1, 21. Besides homosexual men, other groups (intravenous drug users, haemophiliacs) presented a similar syndrome in the USA and Europe. In Africa, AIDS spread rapidly in young adults of both sexes as well as in infants of infected mothers. In 1983-84, the pathogenic virus was first isolated in France and then in the USA [3, 41. The main targets of the human immunodeficiency virus (HIV) are the T-helper lymphocytes, which are infected through the surface CD4 receptor that is recognised by the viral envelope glycoprotein gp120 [5-71. Some monocytes and macrophages also express the CD4 receptor and may also be infected by HIV [8, 91. The virus causes the destruction of CD4 lymphocytes by direct cytolysis, syncitia formation, as well as by other immune and auto-immune mechanisms [ 10-131. The result is progressive and severe impairment of cellular immunity. In addition to the T-cell deficit, HIV causes important disorders in humoral immunity. HIV proteins trigger B-cell proliferation either in a mitogenic or an antigen-specific manner [14, 151. The mitogenic response may be directly caused by the virus (independently of accessory cells), and also by the release of cytokine, such as interleukin 6 [16, 171. B-cell activation is characteristic of patients with mild as well as severe manifestations of HIV infection [ 181. Infected subjects display increasing serum levels of irnmunoglobulins, circulating immunocomplexes and also an increased number of peripheral lymphocytes spontaneously secreting immunoglobulin [ 19, 201. In addition, seropositive individuals develop a persistent generalised lymphadenopathy (PGL) in approximately 30% of the cases. This lymphadenopathic syndrome is characterised by an exuberant hyperplasia of the germinative centres, where B-cell maturation occurs, with polyclonal B-cell proliferation [21, 221. Severe immunodeficiency together with chronic antigenicimitogenic stimulation has been associated with lymphoid malignancies [23-271. Thus, HIV infection may be considered as a prelymphomatous state. The first cases of Burkitt’s lymphomas (BL) in homosexual men were reported in 1982 [28, 291. In 1983, with the observation of several cases of aggressive non-Hodgkin lymphomas (NHL) in risk groups for AIDS, a definitive relation between NHL and AIDS was established [30]. This association was further confirmed epidemiologically [3 1, 321. In 1985, the inci