The role of products of the human HLA-DR locus (Ia molecules) in in vitro M. leprae driven lymphoproliferation.

We analysed the role of Ia molecules in T cell activation with M. leprae by using two hybridoma monoclonal antibodies D1-12 and D4-22 with specificity for non-polymorphic isotypes NG-1 and NG-2 respectively on the HLR-DR molecular framework. The results show that the addition of either monoclonal antibody up to 3 days after onset of culture significantly blocks the in vitro M. leprae driven lymphoproliferation. The mechanism of suppression appears to be due to a combination of steric hindrance and a vigorous suppressor signal from anti-Ia treated macrophages. The possible implications of these results are discussed.