Therapeutically depleting post-resolution macrophages, blocking their secretion of PGE2 or antagonising the predominant PGE2 receptor expressed on T cells, EP4, all resulted in a reduction in CD4+/CD44+/CD62L-/CD27+ early effector memory T cells and their expression of CD103 for up to six weeks post-infection. The gene discussed is PTGER4; the disease is infection.