Role of Th-1 lymphocytes in the development of protective immunity against Mycobacterium leprae. Analysis of lymphocyte function by polymerase chain reaction detection of cytokine messenger RNA.

The patterns of lymphokine mRNA expression during the development of protective immunity to Mycobacterium leprae after intradermal vaccination of mice with killed M. leprae were studied. Using a polymerase chain reaction-based technique for detecting mRNA expression in small numbers of cells, we observed changes in the mRNA expression of a number of cytokine genes in the lymph nodes draining the site of vaccination. In particular, IL-1 (-alpha and -beta), IL-2, TNF (-alpha and -beta), and IFN-gamma mRNA were readily detected, whereas IL-3, IL-4, IL-5, IL-6, IL-7, and granulocyte-macrophage colony-stimulating factor mRNA were not detected, or were detectable only at very low levels. This is consistent with the selective activation of Th-1 Th cells. The effect of in vitro exposure of these cells to the immunizing Ag was also investigated; again, IL-1, IL-2, TNF, and IFN-gamma mRNA were abundant, but in addition, IL-3, IL-6, and granulocyte-macrophage colony-stimulating factor mRNA were greatly increased, suggesting an important role in the recall response.