Fig. 4.

Mature T cells of old PAPPA^−/− mice are functional. Splenocytes from 2-/18-month-old wild-type (WT) and PAPPA^−/− (KO) mice (7 per group) were stimulated with anti-CD3 and anti-CD28, or IgG control; cells and supernatants harvested after 5 days. (A) T cell phenotypes were examined by flow cytometry. Histograms shown were representative profiles of CD3/CD28-stimulated cells for the expression of Ki67, CD25, and CD69 in electronically gated CD3⁺CD4⁺ T cells. Control cultures, irrespective of genotype and age, incubated in IgG had expression profiles that were superimposable with histogram of IgG isotype staining controls. Similar expression levels for these molecules were seen for CD3⁺ CD8⁺ T cells. (B) Expression of the T helper antigen CD154 was also examined by flow cytometry. IgG/IgM production in the culture supernatants was measured by ELISA. (C) Cytokine content of the supernatants was measured by the Luminex system. Tall white and gray bar graphs (5 mice per group) in B and C are weighted means of triplicate measurements (± SEM) of CD3/CD28-stimulated cells. Hatched bars inside the tall bar graphs were measurements from control cells incubated in IgG.