All are true about bacterial killing except
(AIIMS May 10)
|A||MPO helps in formation of OCl|
|B||NADPH helps in formation of superoxide ion|
|C||Chediak hegashi has failure of phagolysosome formation|
|D||Immune deficiency in brutons agammag-lobulinemia is not related to opsonization|
Immune deficiency in brutons agammaglobulinemia is not related to opsonization
a. Myeloperoxidase(MPO) is a peroxidase enzyme present in neutrophils. It is a lysosomal protein stored in azurophilic granules of the neutrophil.
b. MPO produces hypochlorous acid (HOCl) from hydrogen peroxide (H2O2) and chloride anion (Cl-) during the neutrophil's respiratory burst. It requires heme as a cofactor.
c. NADPHhelps in formation of superoxide ions by reacting with oxygen in the presence of NADPH oxidase.
d. These superoxide radicals are used by immune cells to destroy pathogens in the respiratory burst.
e. Chédiak-Higashi syndrome is a rare childhood autosomal recessive disorder that affects multiple systems of the body. arises from a mutation in the lysosomal trafficking regulator gene, LYST. It is a disease with impaired bacteriolysis due to failure of phagolysosome formation.
f. X-linked agammaglobulinemia(XLA), or Bruton agammaglobulinemia, is an inherited immunodeficiency disease caused by mutations in the gene coding for tyrosine kinase (BTK).
g. BTKgene defect has been mapped to the long arm of the X chromosome. BTK is critical to the maturation of pre–B cells to mature B cells..
h. Without mature B lymphocytes, antibody-producing plasma cells are also absent. Opsonization involves the binding of an opsonin, i.e., antibody, to a receptor on the pathogen's cell membrane.
i. After opsonin binds to the membrane, phagocytes are attracted to the pathogen. The Fab portion of the antibody binds to the antigen, whereas the Fc portion of the antibody binds to an Fc receptor on the phagocyte, facilitating phagocytosis.
j. Due to antibody depletion, opsonization is defective and the patient is susceptible to various pyogenic infections, especially due to S. pneumoniae and H. influenzae.