MYD88 and pneumococcal infection: In Streptococcus pneumoniae infections, KLF4 expression in macrophages is induced only by viable pneumococci that establish direct contact with host cells and release autolysin N-acetylmuramoyl-L-alanine amidase (LytA)-dependent DNA, partially mediated via Toll-like receptor (TLR) 9 and the adaptor protein myeloid differentiation primary response 88 (MyD88) (26).