CD4 and CD8 expression by dendritic cell subtypes in mouse thymus and spleen

The dendritic cells (DC) of mouse spleen and thymus were examined for expression of CD4 and CD8, Provided care was taken to avoid selective extraction or selective depletion of DC subpopulations, three main types of DC were detected in mouse spleen: a major new population of CD4(+)8(-) DEC-205(low) CD11b(high) DC, together with the previously described CD4(-)8(-) DEC-205(low) CD11b(high) DC and CD4(-)8 alpha alpha(+) DEC-205(high) CD11b(low) DC. The CD4 on the surface of the CD4(+) splenic DC subpopulation was produced by the DC themselves, and CD4 RNA transcripts were present. Likewise, the CD8 alpha on the surface of the splenic CD8(+) DC was shown to be a product of the DC themselves, in agreement with earlier evidence, All three spleen DC types would be considered as mature, based on expression of CD80, CD86, and CD40 as well as on T cell stimulating function, Mouse thymuses appeared to contain two DC types; both were DEC-205(high)CD11b(low), but they differed in the level of CD8 alpha alpha expression. However, as well as this authenticated marker expression, immunofluorescent staining was also found to reflect a series of artifacts, due to the autofluorescence of contaminating cells and due to pickup of CD4 and CD8 alpha beta. By constructing mice chimeric for the hemopoietic lineages using mixtures of wild-type bone marrow with CD4(null) or CD8 alpha(null) bone marrow, a marked pickup by thymic DC of Ags derived from thymocytes was demonstrated.