Final answer:
Serum sickness is a systemic type III hypersensitivity reaction that typically does not manifest on first exposure to an antigen due to a lag in antibody production. It can occur more rapidly upon second exposure, usually within 1-3 weeks, because the immune system has been previously sensitized, leading to immediate antibody response and immune complex deposition.
Step-by-step explanation:
Serum Sickness and Hypersensitivity Reactions
Serum sickness is a systemic type III hypersensitivity reaction that typically occurs after exposure to certain proteins, like animal-derived antibody preparations, certain drugs, or microbial antigens during chronic infections. This condition is associated with the immune system's adaptive immunity. Upon first exposure to a novel protein antigen, there is a lag period of approximately 10 days, where naïve B cells engage in processes such as antigen binding, processing, presentation, and activation, leading to clonal proliferation and differentiation into plasma cells. IgM levels peak around 14 days post-exposure, followed by IgG. Serum sickness like symptoms usually do not occur during this first exposure due to the lag in antibody production.
Upon second exposure to the same antigen, serum sickness symptoms can occur much more rapidly, generally within 1-3 weeks. This is because the immune system has already been sensitized to the antigen, and memory B cells can promptly produce specific antibodies, mainly IgG, which form immune complexes with the antigen. These complexes can deposit in tissues, leading to inflammation and tissue damage, with symptoms like fever, rashes, arthritis, and potentially glomerulonephritis or hepatitis. It is essential to monitor serum antibody levels to discern the phases of the immune response and diagnose new infections accurately.