1. Bills recurrent infections were due almost exclusively to Streptococcus and H

Question

1.       Bills recurrent infections were due almost exclusively to Streptococcus and Haemophilus species. Theses bacteria have a slimy capsule composed primarily of polysaccharide polymers, which protect them from all direct attack by phagocytes. Humans make IgG2 antibodies against theses polysaccharide polymers. The IgG2 antibodies opsonize the bacteria by fixing complement on their surface, thereby facilitating the rapid uptake of theses bacteria by phagocytic cells. What other genetic defect in the immune system might clinically mimic X-linked agammaglobulinemia?

Explanation / Answer

X-linked agammaglobulinemia is a genetic disorder in which there is an absence of B lymphocytes, mature circulating B cells proliferate after the interaction with antigens and then differentiate into plasma B cells which secrete antibodies. a person with this defect will have an abnormalities in antibody synthesis.

pyogenic(pus forming) bacteria are the majaor cause of infection in X-linked agammaglobulinemia and as we know pus consist largely neutrophills. production of antibodies is normal host response to pyogenic infection, in which there is a coating of bacteria occurs and then complement fixation, thereby it enhances uptake of bacteria into phagocytic cells such as macrophages and neutrophills.

C3 complement deficiency is an another autoimmune disorder that might clinically mimic X-linked agammaglobulinemia ( in this deficiency there is no iC3b to bind to CR3). C3 is a mojor opsonin , which in deficiency causes recurrent pyogenic infections. it is an alternative pathway of complement system which is initiated by fragments of the complement component C3.

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