Detection of a minor stimulating product involved in secondary allogenic proliferation of human lymphocytes in vitro]

In a family with a shared parental haplotype studied in MLR I and II we report that: 1) A secondary proliferation can be induced without a primary positive MLR; 2) In these conditions a minor determinant activating secondary proliferation is detected; 3) No significant association of this product with the available makers (HLA-A, B, C, D, Ly-Li) of the HLA region has been found so far; its localisation within or outside the MHC is under investigation.