Fc gamma receptor and complement system (FcγR and Complement)

The target complex consisting of Fc gamma receptors (FcγRs) and complement components represents the primary immunological effector system for clearing Haemophilus influenzae type b (Hib) infections. This system is activated when anti-polyribosylribitol phosphate (PRP) IgG antibodies, typically induced by Hib conjugate vaccines, bind to the bacterial polysaccharide capsule (Peltola, 2000). The Fc region of the bound IgG then interacts with FcγRs (primarily FcγRIIa) on phagocytic cells like neutrophils and macrophages to trigger opsonophagocytosis (Insel et al., 1986). Simultaneously, the IgG-PRP complex activates the classical complement pathway via C1q, leading to the deposition of C3b opsonins and potential membrane attack complex formation (WHO, 2013). This dual recruitment of cellular and humoral innate immunity is essential for preventing invasive Hib diseases such as meningitis and sepsis. Therapeutic interventions targeting this pathway primarily include conjugate vaccines that elicit high-affinity anti-PRP IgG to leverage these host defense mechanisms (Heath, 1998).

Other names

Fc gamma receptorsComplement componentsAnti-PRP IgG effector complexHib opsonization pathwayFc gamma receptor-mediated phagocytosis system

Anti-PRP IgG antibodies bind to the Hib capsule, facilitating bacterial clearance through Fc gamma receptor-mediated phagocytosis and classical complement pathway activation.