Antigen specific immune responses mediated directly by activated immune cells rather than by the production o… - DSSSB - 29 August 2019 (Shift-2)

DSSSB - 29 August 2019 (Shift-2)

Applied Microbiology & Infection control

Easy

Appeared in: DSSSB - 29 August 2019 (Shift-2)

Explanation

Cellular immunity, also known as cell-mediated immunity, is an antigen-specific immune response that does not involve antibodies.
It is primarily driven by activated T-lymphocytes (T-cells), which act directly to eliminate pathogens or infected cells.
Key cells involved are T-helper (CD4+) cells that orchestrate the response, and Cytotoxic T-lymphocytes (CD8+) that kill infected cells.
This system is crucial for defending against intracellular pathogens like viruses, some bacteria, fungi, and for destroying cancerous cells.

Option B: This is a synonym for humoral immunity, which relies on antibodies. The question explicitly states the response is 'rather than by the production of antibodies'.
Option C: This term is too broad and non-specific. Both cellular and humoral immunity are 'antigen-dependent' as they are initiated by the recognition of a specific antigen.
Option D: Humoral immunity is the arm of the adaptive immune system mediated by antibodies produced by B-lymphocytes. This is the direct opposite of the process described in the question.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Difference between Cellular and Humoral Immunity as background academic context rather than a clinical decision trigger.
Understanding the difference is critical in managing immunocompromised patients. For example, HIV specifically targets and destroys CD4+ T-helper cells, crippling the cellular immune response and leaving the patient vulnerable to opportunistic infections.
In organ transplantation, the major threat is a cell-mediated rejection, where the recipient's T-cells attack the foreign tissue. Immunosuppressive drugs primarily target T-cell activation to prevent this.
What if? If a patient is bitten by a venomous snake, the immediate threat is the toxin circulating in the blood. The most effective immediate treatment is passive humoral immunity, i.e., administering antivenom containing pre-made antibodies to neutralize the toxin, as a cellular response would be too slow and ineffective against a soluble toxin.

How to Approach the Question

First, break down the question stem to identify the key defining phrases: 'mediated directly by activated immune cells' and 'rather than by the production of antibodies'.
Recognize that these two phrases describe the fundamental difference between the two main branches of the adaptive immune system.
Evaluate the options based on these definitions. 'Cellular immune response' directly corresponds to the description of a cell-led action.
Eliminate 'Humoral immune response' and 'Antibody dependent response' as they both refer to antibody-mediated immunity.
Dismiss 'Antigen dependent response' as it is a general characteristic of all adaptive immunity, not a specific type of response, making it a distractor.

Concept Tested & Keywords

Concept Tested: Difference between Cellular and Humoral Immunity
Stem keywords: Antigen specific, immune responses, activated immune cells, not antibodies
Lead-in keywords: are called

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