To better describe the process of neutrophil entry we have used two murine mastitis model systems; (1) MPEC challenge in C57BL6 TLR2-deficient mice where both IBCs and intraepithelial neutrophils were observed (Figures 1, 3A, Additional file 1), and (2) a novel model where we infected the mammary gland of C57BL/6 lactating mice with the non-pathogenic laboratory strain E. coli DH5α, which is unable to replicate in the mammary gland (Additional file 4A) or to survive in neutrophils. The gene discussed is TLR2; the disease is mastitis.