Question

B-lymphocytes are primarily involved in?

A) Humoral immunity
B) Autoimmune disorders
C) Graft rejection
D) Cell-mediated immunity

Answer 1

Hint: B- cells mature in the bone marrow in many mammalian species, including humans(in birds bursa of fabricus), and express membrane-bound antibodies. Contact with an antigen induces naïve B cells( cells that have not been exposed to an antigen) to proliferate and differentiate into effector cells known as plasma cells and memory cells.


Complete step-by-step answer:
Effector cells carry out specific functions to combat the pathogen, while memory cells persist in the host, and when re-challenged with the same antigen, respond faster and more efficiently. B cells also serve as antigen-presenting cells(APCs). Defense against microbes that is mediated by B cells is called humoral immunity.
Cell-mediated immunity is called cellular as its effectors were such cells that comprise the immune system. It is affected by T-cells, APCs, and target cells. It cannot be transferred without T-cells.
Autoimmunity: As we know the immune system is capable of distinguishing self from non-self or foreign. This capability helps it to recognize only foreign particles and act against them. However, sometimes this capability to distinguish self from non-self is faulty. As a result immune system fails to recognize self-antigens and thus acts starts to against self-antigens. This malfunctioning of the immune system leads to the destruction of the host’s tissues and organs. This condition when the body’s immune system attacks and destroys its tissues and organs, is called autoimmunity. And its disorders are called auto-immune disorders.
Graft rejection: Transplantation of tissues or organs from one individual to a genetically non-identical individual invariably leads to rejection called graft rejection of the transplant due to an adaptive immune response.


Therefore the correct answer is Option A.
Note: Humoral immunity neutralizes and eliminates extracellular pathogens, which can then be killed inside phagocytes. However, antibodies cannot attack pathogens that survive inside phagocytes and other cells. T cell-mediated immunity evolved to provide defense against such pathogens.