LTF and pneumococcal infection: Therefore, a reason behind the elevated protective immune responses to invasive pneumococcal infections in the group of mice immunized with a combination of rPspA with PhtD might be the production of a high level of IgG antibodies compared to antigen alone and the synergistic effect of anti-PhtD and anti-PspA specific IgGs to prevent both antigen-mediated inhibitory functions of the host’s complement system and lactoferrin.