Polymorphism for RhT3, a CD3-like cell surface antigen, expressed on rhesus monkey T lymphocytes.

Area of Science:

• Immunology
• Primate genetics

Background:

• The FN18 monoclonal antibody identifies RhT3, a rhesus monkey homologue of the human CD3 antigen found on mature T cells.
• RhT3 exhibits polymorphism, with FN18 showing reactivity in only a portion of the rhesus monkey population.

Purpose of the Study:

• To investigate the genetic basis and functional implications of RhT3 polymorphism in rhesus monkeys.
• To determine the inheritance pattern and potential association of RhT3 expression with immune status.

Main Methods:

• Immunofluorescent staining of peripheral blood lymphocytes using the FN18 antibody.
• Analysis of RhT3 expression in relation to sex, age, MHC class I expression, and T-cell numbers.
• Family studies to elucidate inheritance patterns.
• Intracellular staining and cell proliferation assays with mitogens.

Main Results:

• FN18 non-reactivity (negative phenotype) was observed in 2.7% of the rhesus monkey population and appeared to be a stable trait.
• RhT3 non-expression was not linked to immunodeficiency, sex, age, or MHC class I expression.
• Family studies suggested an autosomal dominant inheritance pattern for RhT3 expression.
• Functional T-cell assays indicated that RhT3 molecules are present and functional even in FN18 non-reactive animals.
• Intracellular staining revealed polymorphism at the epitope level.

Conclusions:

• RhT3 polymorphism in rhesus monkeys is likely determined by an autosomal dominant gene.
• The observed polymorphism affects the epitope recognized by FN18 and does not impair T-cell function or cause immunodeficiency.
• This finding contributes to understanding T-cell antigen variability in non-human primates.