Which one of the following statements best describes the role of B cells and T cells in the human body?

(a) They protect the body from environmental allergens.

(b) They alleviate the body’s pain and inflammation.

(d) They protect the body from the diseases caused by pathogens.

Explanation

The correct answer is d) They protect the body from the diseases caused by pathogens.

B cells and T cells are two types of lymphocytes that play critical roles in the adaptive immune system.
B cells mature in the bone marrow and secrete antibodies that recognize and bind to antigens on pathogens or infected cells. Antibodies mark pathogens for destruction by other immune cells.
T cells mature in the thymus gland and directly attack infected or cancerous cells. There are several types of T cells:
- Helper T cells activate B cells to produce antibodies and also activate cytotoxic T cells.
- Cytotoxic T cells directly kill infected or cancerous cells.
- Regulatory T cells suppress immune responses and prevent autoimmunity.
Both B cells and T cells protect the body by recognizing specific antigens on pathogens like bacteria, viruses, fungi or parasites. They mount an adaptive immune response to eliminate the pathogen and prevent disease.
Therefore, the statement that best describes their role is “They protect the body from the diseases caused by pathogens.”
Options a, b and c are incorrect:
- B and T cells do not protect against environmental allergens or alleviate pain/inflammation. That is done by other immune cells like mast cells, basophils, neutrophils.
- They also do not act as immunosuppressants. Regulatory T cells suppress immune responses, but most T cells and B cells stimulate immune responses.

B cells and T cells, collectively known as lymphocytes, are the central cells involved in adaptive immunity.
B cells:
- Originate and mature in bone marrow
- Express B cell receptors (BCRs) on their surface that can bind to specific antigens.
- When a naïve B cell encounters its specific antigen, it proliferates and differentiates into antibody-secreting plasma cells and memory B cells.
- Plasma cells secrete antibodies that mark pathogens for destruction. Memory B cells persist after infection and facilitate faster secondary responses.
T cells:
- Originate in bone marrow but mature in thymus gland.
- Express T cell receptors (TCRs) that recognize antigen fragments bound to MHC molecules on cell surfaces.
- Main types:
  - Helper T cells activate B cells, cytotoxic T cells and macrophages.
  - Cytotoxic T cells directly kill infected or cancerous cells.
  - Regulatory T cells suppress immune responses and prevent autoimmunity.
- Also include memory T cells that persist after infection and provide long-term protection.
Both cell types undergo gene rearrangement to produce diverse receptors capable of recognizing millions of distinct antigens.
They provide:
- Immunological memory
- Specificity
- Adaptability
Deficiencies in B cells or T cells lead to immunodeficiencies like SCID, highlighting their key role.