Fig. 1. Ptpn22^-/- T cells show greater expansion in numbers than do WT cells in vivo, but they do not have increased T_H2 helper activity.

(A) Naïve T cells purified from WT (CD45.1⁺) and Ptpn22^-/- (CD45.2⁺) lymph nodes were labeled with CFSE and injected i.v. into Rag1^-/- recipient mice (n = 5) at a 1:1 ratio (4 x 10⁶ cells/mouse in total). The abundances of CD44 and CD25 on the surface of transferred T cells were comparable before injection, and the proportions of WT (CD45.1⁺) and Ptpn22^-/- (CD45.2⁺) cells in the blood of recipients were monitored on day 1 (WT = 53 ± 8% and Ptpn22^-/- = 43 ± 9%; values are means ± SD). After 14 days, the lymph nodes of recipient mice were analyzed by flow cytometry for the proportions of CD45.1⁺ and CD45.2⁺ T cells. Representative dot plots and ratios of WT (CD45.1⁺) to Ptpn22^-/- (CD45.1^-) cells are shown. Each point represents an individual animal; data are means ± SEM. Results are representative of two individual experiments. (B) Amounts of PTPN22 mRNA were assessed in CD4⁺ T cells from lymph nodes of WT mice that were sorted to give CD25^-CD44^lo, CD25^-CD44^hi, and CD25⁺ cells, as well as in total thymus cells. Values are expressed relative to the amounts of Hprt mRNA. Each point represents an individual animal (n = 3 mice). (C) Groups of WT and Ptpn22^-/- mice (n = 5 mice of each genotype) were immunized with 2000 S. mansoni eggs on day 0, followed by a boost of 1000 eggs on day 49. Sera from tail bleeds were assessed for SEA-specific IgG at various time points by ELISA. Graph represents the mean EC50 values values ± SEM. *P < 0.05, ***P < 0.005.