Q.Why is opsonisation efficient in phagocytosis ?

Opsonisation marks pathogens with antibody/complement molecules that phagocytic cells can specifically recognise and bind, greatly speeding up and improving the efficiency of phagocytosis.

Phagocytic cells like macrophages and neutrophils can engulf pathogens directly, but this process (unassisted phagocytosis) is relatively slow and inefficient, since the phagocyte has to physically recognise general, non-specific features of the microbial surface. In opsonisation, antibodies (especially IgG) and/or complement proteins (e.g., C3b) bind specifically to antigens on the pathogen's surface, coating it. Phagocytes carry specific receptors (Fc receptors for the antibody's Fc region, and complement receptors) on their surface that recognise and bind tightly to these opsonin-coated pathogens. This specific, high-affinity attachment anchors the pathogen firmly to the phagocyte surface, triggering more effective engulfment (phagocytosis) and destruction than would occur wit …