Date of Award:

5-1994

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Mark C. Healey

Committee

Mark C. Healey

Committee

Shiguang Yang

Committee

Kathleen R. Rasmussen

Committee

Reed P. Warren

Abstract

The purpose of this study was to quantitate the populations o f lymphocytes in the spleens and intestines of normal and immunosuppressed adult C57BL/6N mice that were noninfected or infected with Cryptosporidium parvum. This was accomplished by using the following methodologies: immunohistochemistry, ELISA-spot assay, and flow cytometry.

Mice in groups 1 and 2 were immunosuppressed, but only group 2 was infected. Mice in group 3 were only infected, whereas group 4 served as the normal control. Mice were immunosuppressed with dexamethasone (DEXI at a dosage of 125µg/mouse/day. Infected mice received 106 oocysts per os. The numbers of lymphocytes were monitored from day 0 to day 18 postinfection. Flow cytometry using antibodies directed against CD4+ and CDS+ T cells (helper and cytotoxic, respectively) and B cells (expressing IgG, IgM, and IgA receptors) revealed that C. parvum did not evoke an alteration in the phenotypic profile of lymphocytes within spleens or Peyer's patches (PP) of mice in groups 2 and 3 that was statistically different from groups 1 and 4. Immunosuppressed mice (groups 1 and 2) had significantly fewer lymphocytes (bearing CD4+, IgG, IgM, and IgA receptors) within the spleen when compared with mice in groups 3 and 4 (P<0.05). Splenic leucocytes expressing macrophage (CD11b) and CD8+ receptors failed to respond to DEX. Moreover, the CD4+ to CD8+ cell ratio was decreased in the spleens of immunosuppressed mice. After 6 days of DEX administration, the percentage of T cells (CD8+) and macrophages within the PP was significantly higher than nonimmunosuppressed mice (P<0.05). Administration of DEX had no apparent effect on B (bearing IgG, IgM, and IgA receptors) and T lymphocytes (CD4+) present within the PP. However, DEX treatment was associated with a lower CD4+ to CD8+ lymphocyte ratio within the PP. Preliminary studies using immunohistochemistry demonstrated that lymphocytes bearing IgA receptors are significantly less in mice that received DEX for 20 (P<0.05), whereas the number of IgG and IgM receptor-bearing lymphocytes was not significantly affected.

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