MHC control of cell position in vitro.

Two-dimensional sorting-out behaviour (segregation) in mixtures of pulmonary endothelial cell lines derived from congenic strains of mice was examined using dense confluent cultures in which mitosis is rare. Cell MHC type was detected by autoradiographic labelling or by immunofluorescence techniques. For autoradiography cultures of one type were previously labelled with [3H]thymidine and one component of the mixed cell types was prepared from these cultures. Autoradiographs were prepared from the fixed cultures. Counts of contiguous neighbours (labelled or unlabelled around a randomly chosen central labelled cell) were made: these were analysed statistically using a new model for such a system. The results show that segregation of a clustering type took place if the alleles of the D locus in the H-2 complex were mismatched in the mixed strains, but that matching at the IC locus (or some locus to the right of IJ) overrides the effect of D mismatch. After 2 days culture sorting-out was easily detectable when the cells were stained for their histocompatibility antigens and groups of up to 12 cells of the same type were associated together.