IgE-bearing cells and epsilon-specific mRNA in lymphoid organs of two children with AIDS

Abstract

To characterize the cellular basis of IgE responses in HIV-positive (HIV+) children, we obtained central (bone marrow [BM], thymus) and peripheral (Peyer's patches [PP], mesenteric [MLN], and other lymph nodes [OLN], spleen), lymphoid organs from two children with AIDS (females, 2 and 8 years old), and from a non-HIV-infected trauma victim (female, 5 years old) at autopsy. PP were obtained from one of the HIV+ children (2 yr old) and from the non-infected child, but no PP were detected in small intestine of the 8-yr-old HIV+ child. Numbers of lymphocytes bearing surface IgE, CD19, CD3, CD4, and CD8 in lymphoid organs were determined (flow cytometry) and evaluated for expression of epsilon-specific (E) mRNA (RT-PCR). Thymus and MLN of the HIV+ child without PP contained high numbers of IgE+ (34% and 41%, respectively) and CD19+ (32% and 28%, respectively) cells; IgE+ cells were not found in any other organ. In contrast, in the HIV+ child with PP, IgE+ cells were detected in all organs, except BM. The thymus of this child contained fewer CD19+ cells (7%). However, in both HIV+ children, all lymphoid organs, including thymus, contained E mRNA. Because numbers of IgE+ cells often far exceeded numbers of CD19+ B cells, and because CD8+ T cells predominated in all organs, some of the IgE+ cells were probably CD8+ T cells with cytophilic IgE and may include IgE-specific regulatory and/or memory T cells. IgE responses were not detected in the healthy trauma victim nor were B cells found in thymus. The data suggest that during HIV infection, IgE+ B cells may be found in thymus and that synthesis of IgE may occur in all lymphoid organs except BM.