Autoimmunity - Immunodeficiency Disorders

SCID is a severe congenital immunodeficiency in which both T-cells and B-cells are absent or highly defective, causing extreme vulnerability to infections.

• It is a primary immunodeficiency disorder present from birth.
• Both major arms of immunity are affected, so body defence becomes extremely weak.
• Even ordinary infections may become serious or life-threatening.

DiGeorge syndrome is a congenital immunodeficiency associated with defective development or absence of the thymus, resulting mainly in T-cell deficiency.

• It is a primary immunodeficiency disorder.
• Since the thymus is poorly developed or absent, proper maturation of T-cells does not occur.
• B-cells may be present, but cell-mediated immunity remains impaired due to a lack of functional T-cells.

Agammaglobulinemia is a congenital disorder in which B-cell function is deficient, leading to markedly reduced antibody production while T-cell activity remains relatively normal.

• It is a primary immunodeficiency disorder.
• The major defect lies in the B-cell component of immunity.
• Because antibodies are not formed adequately, recurrent infections are common.
• T-cell function is generally preserved.

AIDS is a serious acquired immunodeficiency disorder caused by HIV, in which the immune system becomes progressively weakened and the body becomes highly susceptible to opportunistic infections.

• It is a secondary or acquired immunodeficiency disorder.
• HIV targets important immune cells and gradually weakens immune defence.
• As immunity declines, the person becomes vulnerable to infections that a healthy immune system can often control.
• It is medically and exam-wise important because it links immunology with public health.