Figure 5.

LPS treatment enhances the suppressor function of Treg. (a) Suppressor efficiency of CD4⁺ CD25⁺ is greatly enhanced upon exposure to LPS. Sort-purified CD4⁺ CD25⁺ T cells were maintained in culture in medium supplemented with anti-CD3 and either LPS for 3 d followed by 3 d with IL-2 (LPS/IL-2) or with IL-2 for 6 d (IL-2). The same cell population not submitted to culture was used as reference control (fresh). Proliferation of CD4⁺ CD25⁻ stimulated with anti-CD3 and APC in the presence of increasing numbers of these CD4⁺ CD25⁺ cells was monitored on day 3. The percent of inhibition ([cpm in control − cpm in experiment]/cpm in control) is plotted versus the ratio of CD4⁺ CD25⁺/CD4⁺CD25⁻ cell number at the origin of the culture. (b and c) LPS treatment of CD4⁺ CD45RB^low CD25⁻ cells reveals their suppressor functions. Sort-purified CD4⁺ CD45RB^low CD25⁻ cells were tested in suppression assays after 6 d culture (b) or after only 3 d exposure to LPS and anti-CD3. Suppression by CD4⁺ CD25⁺ treated similarly is also shown. (c) Freshly isolated CD4⁺ CD25⁺ and CD4⁺ CD45RB^low CD25⁻ served as control. Nomenclatures are as described in a. Each measurement has been performed at least twice on independent cell samples and resulted in similar curves.