New Insights into the Immune Response to Pneumococci

Infection by Streptococcus pneumoniae (the pneumococcus) is associated with enormous morbidity and mortality worldwide and this bacterium remains the commonest cause of pneumonia, meningitis and otitis media. While immunity to pneumococcal disease has been widely accepted to depend mainly on the humoral arm of the immune system recent studies have shown a critical role for cellular immunity, specifically T lymphocytes (T cells), that is independent of antibody, in the prevention and clearance of pneumococcal infection. Here we review the evidence that supports the importance of T cells, specifically CD4+, CD8+ and regulatory T cells, in host responses to pneumococcal infection.