CD44 and infection: Increased MDM activation coincided with significantly increased numbers of CD44+CD62L−CD4+ T cells in lungs of anti-Ly6G–treated mice compared with isotype controls by 26 days after infection (Fig. 6 e) and increased frequency of CD4+ T cells within lung lesions as early as 20 days after infection, which was greatly augmented by day 26 (Fig. 6, f and g).