In contrast, mice that had been immunized with dead pneumococci 4 weeks before the live challenge were strongly protected (Fig.5b), consistent with the optimal protection provided by the T15 germ-line idiotype anti-phosphocholine antibody.18 Autologous mouse CRP is therefore required for innate resistance to pneumococcal infection before sufficient specific antibodies are produced, but can be replaced by isolated human CRP or a previous anti-pneumococcal immune response. The gene discussed is CRP; the disease is pneumococcal infection.