Tr-1 conversion depends on TCR signaling and a direct T-/B-interaction through CD40/CD40L and B7-1/CD28. B cell-induced Tr-1 cells RAD001 in vitro acquire suppressive activity in vitro and in vivo. In addition, systemic injection of Pam2 lipopeptides (a TLR-2 ligand) induced IL-10 in a TLR2-dependent manner [31]. The Pam2 lipopeptides increased the frequencies of Foxp3+CD4+ regulatory T (T reg) cells in a TLR2- and IL-10-dependent manner.

Then, the possibility that human OMV vaccination induced T regulatory cells which suppressed B cell activation cannot be ruled out and further investigation may be conducted in the future. Interesting enough, we have previously reported a negative dose-effect on booster bactericidal antibody response, in that mice immunised with four doses of VA-MENGOC-BC®, but not with two or three AZD8055 chemical structure doses, responded less well to the booster dose compared with the primary series [14]. In conclusion, this study suggests that vaccination with the VA-MENGOC-BC® induced a robust immune response after three injections of vaccine. Vaccination induced the generation and activation of memory T-cells

after primary and booster schedules but failed to maintain a memory B-cell population at a stable size and/or functionality. The weak boosting antibody response reinforces suboptimal recall functions of the remaining memory B-cell population. More studies are needed in view of the scarce knowledge about cellular mechanisms of antibody response and development of immunological memory by meningococcal vaccines. We are thankful to Ricardo da Costa Cruz for proof-reading the manuscript. We acknowledge FAPERJ/SR2-UERJ/CAPES very and CNPq for financial support.

This study would not be possible without the consent of the volunteers. “
“The first barriers that microorganisms including viruses must breach for being successful pathogens are imposed by the innate immune system of which the complement system constitutes a major arm [1], [2], [3] and [4]. The complement system comprises of an intricate group of both soluble and cell-associated proteins activated through three major pathways, the classical, alternative and lectin pathways. Complement activation results in the generation of active components, including C3b and C4b, which aid in the assembly of enzymes called as C3/C5-convertases that facilitate downstream cleavage and formation of the membrane attack complex (MAC) capable of lysing pathogens. Additionally, the activation products C3a and C5a show anaphylatoxic and chemotactic properties [5] and also play a role in T cell activation [6], and surface bound complement components derived from C3 interact with specific immune receptors, thus acting as a connecting link with the adaptive immune system [7]. Hence, the complement system exerts assault on pathogens directly by lysis and indirectly by boosting the pathogen-specific immune responses [8].