Benign monoclonal expansion of CD8+lymphocytes in HIV infection

Background-A transient expansion of the CD8+ T cell pool normally occurs in the early phase of HIV infection. Persistent expansion of this pool is obs erved in two related settings: diffuse infiltrative lymphocytosis syndrome (DILS) and HIV associated CD8+ lymphocytosis syndrome. Aim-To investigate a group of HIV infected patients with CD8+ lymphocytosis syndrome with particular emphasis on whether monoclonality was present. Methods-A group of 18 patients with HIV-1 infection and persistent circulat ing CD8+ lymphocytosis was compared with 21 HIV positive controls. Serum sa mples were tested for antinuclear antibodies, antibodies to extractable nuc lear antigens, immunoglobulin levels, paraproteins, human T lymphotropic vi rus type 1 (HTLV-1), Epstein-Barr virus, and cytomegalovirus serology. Lymp hocyte phenotyping and HLA-DR typing writs performed, and T cell receptor ( TCR) gene rearrangement studies used to identify monoclonal populations of T cells. CD4+ and CD8+ subsets of peripheral blood lymphocytes were purifie d to determine whether CD8+ populations inhibited HIV replication in autolo gous CD4+ cells. Results-A subgroup of patients with HIV-1 infection was found to have expan ded populations of CD8+ T cell large granular lymphocytes persisting for 6 to 30 months. The consensus immunophenotype was CD4- CD8+ DRhigh CD11a+ CD1 1c+ CD16- CD28+/- CD56- CD57+, consistent with typical T cell large granula r lymphocytes expressing cellular activation markers. Despite the finding o f monoclonal TCR gene usage in five of 18 patients, there is evidence that the CD8+ expansions are reactive populations capable of mediating non-cytot oxic inhibition of HIV replication. Conclusions-A subgroup of HIV positive patients has CD8+ lymphocytosis, but despite the frequent occurrence of monoclonal TCR gene usage there is evid ence that this represents an immune response to viral infection rather than a malignant disorder.