CHARACTERIZATTON OF HUMAN FETAL INTESTINAL LYMPHOCYTES

Abstract

The characterization of human B and T cell subset development in the fetus has been limited mainly to thymus, liver, bone marrow and spleen. This study compares the lymphocyte subsets of human fetal intestine to that of the normal infant and adult. Monoclonal antibodies identifying T cells (Leu4+), helper/inducer (Leu3a+), cytotoxic/suppressor (Leu2a+), HIA-DR, and B cells were used with the immunoperoxidase technique to quantify cells in the thymus, spleen, liver, small bowel, cecum and colon of two 18-20 week fetuses and normal proximal jejunum of a six month old infant. RESULTS: Like adults, fetal thymus, spleen and intestinal lamina propria (LP) contain Leu3a+ and Leu2a+ lymphocytes, but in contrast to adults, rare intraepithelial lymphocytes (IEL) were noted in the fetus and infant. IgM+ and IgD+ B cells were present in the LP of the infant, but were mostly restricted to lymphoid aggregates in fetal intestine. HIA-DR antigen was absent from the mucosal epithelium of the fetus but present in the infant. CONCLUSIONS: T cells in the LP precede B cell development. Leu3a+ cells predominate in the LP, but Leu2a+ IEL, prevalent in adults, are conspicuously rare in the fetus and infant. HIA-DR is absent from the fetal epithelium, but present in the infant and adult. These findings are consistent with the hypothesis that the presence of IEL and expression of HIA-DR by intestinal epithelial cells is possibly related to exposure to luminal antigenic stimulation.