A non-lymphoma idiotype is indicative and predictive for B cell malignancies in AIDS

The 1F7 idiotype previously defined (J Immunol 147:933;1991 and Eur J Immunol 22:1749;1992) is expressed on antibodies reactive to different proteins of HIV (gp41, p24, gp120). Since serum levels of 1F7 (IgM or IgG) are significantly higher in patients with HIV lymphoma as opposed to HIV-infected individuals, normal controls and non-HIV lymphoma patients, we hypothesized the B-cell neoplasms were the source of the idiotype. However, immunohistochemistry on cryostat sections revealed no 1F7 idiotype signal on neoplastic B-cells nor tumor infiltrative T-cells (n = 8). Interestingly, reactive lymphocytosis adjacent to tumor masses and reactive follicular hyperplastic controls (n = 5) exhibited significant 1F7 reactivity. The reactivity appeared in paracortical and perifollicular lymphoid regions, predominantly regions of B, T and antigen presenting cells in lymph nodes or tonsils. A survey of electrophoretically defined paraproteins with anti-HIV specificities derived from HIV-infected patients showed no Western blot reactivity with the 1F7 anti-idiotypic antibody. Therefore, the idiotype does not appear to be a direct product of B-cell neoplasia or abnormal B-cell proliferation, but is produced by B cell clones responding to HIV infection. This high level of serum 1F7 reactivity could be an important clue in the pathogenesis of HIV lymphomas and confers a highly predictive serological test for HIV lymphoma.