PATHOLOGY

Detailed explanation-1: -IgG antibodies are usually of higher affinity and are found in blood and in extracellular fluid, where they can neutralize toxins, viruses, and bacteria, opsonize them for phagocytosis, and activate the complement system.

Detailed explanation-2: -IgM is the primary antibody produced during an initial antigen challenge.

Detailed explanation-3: -IgM antibodies constitute the major component of the natural antibodies and is also the first class of antibodies produced during a primary antibody response.

Detailed explanation-4: -IgM is the first antibody isotype produced during an immune response and functions as a primary barrier against pathogens. IgM also regulates immune responses. Thus, antigen-specific IgM administered before immunization enhances antibody response, which depends on complement (1).

Detailed explanation-5: -IgM antibodies protect mammals against humoral microbial infection and mediate clearance of cellular debris. IgM activates the immune complement system only after binding to cell-surface antigens.