Changes in mouse MHC expression during the cell cycle of Con A-treated spleen cells

This study was directed at correlating the expression of class I MHC determinants with different segments of the cell cycle by using dual laser flow microfluorometry to measure levels of both DNA and cell surface H-2K(d) or H-2D(d) determinants for single cells. Con A-treated mouse spleen cells were identified as being in the G₂/M or G₀/G₁ phase of the cell cycle on the basis of propidium iodide or Hoechst 33342 dye bound to DNA. Monoclonal anti-H-2 antibodies, indirectly fluoresceinated with goat anti-mouse IgG, were used to detect MHC determinants. The average level of both K(d) and D(d) determinants expressed by G₂/M cells was about 1.6-fold higher than that expressed by G₀/G₁ cells. These observations indicate that the average-size G₀/G₁ and G₂/M cells have the same apparent surface density of K(d) and D(d) determinants, insofar as we estimate that these cells differ in surface area by a factor of about 1.5. We also analyzed the expression of K(d) and D(d) determinants by measuring how they changed as a function of the intensity of forward light scatter from cells. For both G₂/M and G₀/G₁ cells, changes in light scatter intensity were associated with parallel changes in levels of D(d) and K(d) determinants, indicating a common mechanism(s) that controls their cell surface expression.