T-lymphocyte subsets in nude mice with Giardia muris infection.

The aim of this study was to compare the relative percentages of T-lymphocyte subsets in athymic (nude) mice and immunocompetent BALB/c mice, with and without Giardia muris infection. Suspension of mononuclear leukocytes from blood, spleen, and Peyer's patches of uninfected mice were incubated with fluorescent monoclonal antibodies (MAbs) directed against mouse T-lymphocytes (anti-Thy-1.2 MAb), T helper/inducer lymphocytes (anti-L3T4 MAb), or T suppressor/cytotoxic lymphocytes (anti-Ly-2 MAb), and examined by fluorescence microscopy to quantify each of these cell populations. While the percentages of Thy-1.2+, L3T4+, and Ly-2+ lymphocytes are all reduced in nude mice, L3T4+ lymphocytes were found to be especially depleted, resulting in a reversed L3T4+/Ly-2+ ratio (less than 1) in all of the nude mouse tissues examined. BALB/c and nude mouse Peyer's patch T-cell subsets were quantified at various times during enteric Giardia muris infection. Unlike immunocompetent BALB/c mice, nude mice have an impaired ability to clear this infection. It was found that clearance of G. muris infection is associated with a Peyer's patch L3T4+/Ly-2+ ratio of greater than or equal to 2, and that this infection does not alter the percentages of Peyer's patch Thy-1.2+, L3T4+, or Ly-2+ lymphocytes in BALB/c mice or nude mice. The data obtained in the present work and in other studies suggest that the impaired capacity of nude mice to clear G. muris infection results from deficiency of L3T4+ lymphocytes.