Question

Damage to thymus in a child may lead to
A. Loss of cell mediated immunity
B. A reduction in the hemoglobin content in blood
C. A reduction in the amount of plasma proteins
D. Loss of antibody mediated immunity.

Answer 1

Thymus is an organ which is an important part of the immune system. Thymus is the site of maturation of T-cells.

Complete answer:
Option A: T- cells are an important component of cell mediated immunity. T-cells are produced in bone marrow and they migrate to thymus for differentiation and maturation to functional T cells.
And a damage in thymus in childhood will result in defect in T-cell maturation, and through this a loss of cell mediated immunity. This is the correct option.
Cell mediated immunity is the immune response that does not involve antibodies to generate immune response. In cell mediated immunity, the immune response is carried out through: activation of macrophages and natural killer cells, the production of antigen specific cytotoxic T lymphocytes and the release of various cytokines in response to an antigen.
Option B: Hemoglobins are iron rich proteins present in red blood cells ,which facilitate the transport of oxygen and carbon dioxide through blood. Reduction of hemoglobin level is normally associated with iron deficiency, vitamin deficiency etc. This is not related to the thymus. Therefore, this is the incorrect option.
Option C: Plasma proteins are the proteins present in blood plasma which help the transportation of hormones , vitamins etc. They are also a component of the immune system. They are primarily synthesised in the liver and not associated with thymus. Therefore, this is the incorrect option.
Option D: Antibody mediated immunity is carried out by B cells which differentiate into plasma B cells which give rise to different antibodies. Therefore, this is the incorrect option.

Hence, the correct answer is option (A)

Note: The helper T-cells which is a part of antibody mediated immune system also matures in thymus.
Since the major component of antibody mediated immune system is antibody generating cells, this doesn get affected by a defective thymus as much as the cell mediated immunity does.