Specificity of helper T cells for different antigens.

BALB/c nude mice have been injected with 10(6) congenic thymus cells, a number which allows some, but not all mice to respond to any particular T-dependent antigen. These mice have been tested for their ability to respond to three bacteriophages, T4, T7 and phiX, sheep and horse erythrocytes, and alloantigens of C3H and C57BL/6 mice. The number of mice able to respond to each of these antigens was of the same order of magnitude. Sheep and horse erythrocytes showed cross-reactivity at the T cell level, i.e. the responses to these two antigens were not independent. The same was observed for C3H and C57BL/6. Otherwise, the responses were independent showing that the antigens are recognize by different populations of specific helper T cells.