Early detection of the allogeneic effect in the mixed lymphocyte reaction (MLR) by anti-CD3 IgA mouse monoclonal antibody.

MLR is a 6-day routine proliferation assay used to demonstrate HLA disparity between two individuals. However, on day 2 only a negligible proliferation can be detected. In contrast, we found a significant increase of the extent of proliferation if an anti-CD3 IgA antibody was present in the culture. Since the CD3 proliferation pathway cannot be triggered by an antibody of IgA isotype the result was interpreted as a consequence of a synergism between the allogeneic stimulus and the anti-CD3 antibody effect. The level of this proliferation well correlates with the HLA difference, thus suggesting the use of this methodology for a rapid detection of the allogeneic reaction.