Fig 5. A lack of CD4⁺ T cells or of IFNγ increases MHC II⁺ cell infection.

a. Naive mouse lungs were stained for AEC2 (SPC⁺), AM (CD11c⁺), and MHC II. The filled arrow shows an MHC II⁺ AM. White / red co-localization appears as pink. Most MHC II⁺ cells were AEC2 (open arrows). Red / green co-localization appears as yellow. Bars show mean ± SEM of counts for 3 fields of view per section, for 2 sections from each of 2 mice. b. Naive and d5 infected lungs were stained for SPC, MHC II and viral antigens (MHV). In infected lungs, open arrows show MHC II⁺ AEC2, which are uninfected (MHV^-); white filled arrows show infected MHC II⁺ cells, which are SPC^-; the grey filled arrow shows a rare MHV⁺ AEC2 (colocalization appears as white), which is MHC II^-. Fig 5a shows that in naive mice 70% of MHC II⁺ lung cells were SPC⁺. After infection, significantly fewer were SPC⁺ (p<0.001 by Student's 2 tailed unpaired t test), and negligible numbers of MHV⁺MHC II⁺ cells (<5%) were SPC⁺. Bars show mean ± SEM of counts for 3 fields of view per section, across 3 sections from each of 2 mice. c. Mice were depleted of CD8⁺ T cells (αCD8), given optionally either IFNγ neutralizing (αCD8αIFNγ) or CD4⁺ T cell depleting antibodies (αCD8αCD4), then given MuHV-4 i.n. (10⁴ p.f.u.). At d9 lungs were stained for MHV and MHC II. Arrows show dual positive cells. d. For samples as illustrated in c, cells were counted for 3 fields of view per section, across 3 sections from each of 3 mice per group. The proportion of MHV⁺ cells that were MHC II⁺ was significantly increased by αCD4 (p<0.05) but not by αIFNγ (p>0.2). e. MHC II⁺MHV⁺ cells of mice treated as in b were identified as CD11c⁺ or CD11c^-. Cells were counted for 3 fields of view per section, across 3 sections from each of 3 mice per group. αIFNγ significantly increased MHV⁺MHC II⁺CD11c⁺ (p<0.01) but not MHV⁺MHC II⁺CD11c^- cell numbers (p>0.3). αCD4 significantly increased both (p<0.01, p<0.05). f. Example images are shown for the samples counted in e. Arrows show MHV⁺CD11c⁺ cells. g. Staining the same samples for SPC showed that essentially no MHV⁺MHC II⁺CD11c^- cells were AEC2.