Interaction of immune lymphocytes with the mixtures of target cells possessing selected specificities of the H-2 immunizing allele.

Optimum conditions have been found for a specific quantitative absorption of mouse lymphocytes on to allogeneic target cells. Using this technique, it has been established that C3H anti-A lymphocytes immune to the specificities of a single -2 sub-locus (D) were absorbed neither on cells bearing only some of the components of the immunizing complex (DBA/1 and I/St targets) nor on their mixture. Conversely, C57BL anti-A lymphocytes immune to the specificities of two -2 sub-loci (D and K) reacted separately with each of the components on corresponding third-party targets (B10.D2(-2d) and C3H (-2k) as shown both by the direct cytotoxic effect and by the quantitative absorption technique. The results of absorption of these lymphocytes on mixtures of B10.D2 and C3H target cells used in various proportions indicate that C57BL anti-A lymphocytes represent a mixture of two polyvalent' populations in ratio of 1:3. This, together with the previous data indicates that committed' lymphocytes may be polyvalent' and that the initial recognition step of -2 antigens may result from a direct contact between membranes of grafted cells and unprimed' host lymphocytes. Structural matching of the membrane antigenic complex and of normal and immune lymphocytes is suggested as a decisive factor of immunological recognition initiation in a transplantation context.