Chediak higashi syndrome, defect is ?
Ans. is 'a' i.e., Fusion of lysosome Chediak higashi syndrome It is an autosomal recessive disorder. Chediak higashi syndrome is caused due to mutation in the LYST gene. This gene provides instructions for making a protien known as lysosomal trafficking regulator. This protein plays a role in transpo of materials into lysosomes. Lysosomes contain several enzyme. They use these enzymes to kill various microorganism, break down several toxins. During phagocytosis, lysosomes fuse with phagosome, forming phagolysosome. Once the phagolysosomes are formed, lysosomes secrete enzymes to kill the bacterias. Mutation in the LSYT protein disrupts the size, structure and function of lysosomes. Lysosomes cannot fuse with phagosome to form phagolysosome.Thus this syndrome is a disease with impaired bacteriolysis due to impaired phagolysosome formation. As a result, most people with chediak higashi syndrome have repeated and persistent infections, staing in infancy or early childhood. These infections are life threatening. Besides, the granules of lysosomes, the secretory /storage granules of various other cells are also affected. The other cells involved are - Melanosomes of melanocytes Dense bodies of platelets Granules of schwann cells There are giant primary granules in neutrophils and other granules bearing cells. In pigment cells called melanocytes the melanosome become abnormally large so there is reduced production of melanin. Thus people with chediak Higashi syndrome have occulocutaneous albinism i.e the colour of skin, hair and eye is reduced. Abnormality in platelets produce bleeding disorders. Defective granules in schwann cells lead to neurological symptoms e.g. peripheral neuropathy. Most children with chediak Higashi syndrome ultimately reach a stage of the disorder known as accelarated phase (lymphoma like stage). This severe phase of the disease is thought to be triggered by viral infection (E.B.virus). In the accelarated phase, defective white blood cells divide uncontrollably and invade many of the body's organs. The accelarated phase is associated with fever, episodes of abnormal bleeding, overwhelming infections and organ failure. They are usually life threatening and lead to death.
Fusion of lysosome
T-cells
B-cells
Complement