CD5 and influenza: By demonstrating that CD5+ B-1 cells respond to infections with both, influenza and S. typhimurium, the latter previously identified as an exclusive ‘B-1b’ response (Gil-Cruz et al., 2009; Marshall et al., 2012), with rapid downregulation of CD5, the study suggests that pathogen-induced responses by B-1 cells represent responses of CD5+ B-1 cells (Haas et al., 2005; Alugupalli et al., 2003; Alugupalli et al., 2004; Gil-Cruz et al., 2009; Marshall et al., 2012).