RRB Nsg. Superintendent-21 July 2019 (Shift-2nd)
Applied Microbiology & Infection control
Easy
Which cells are that takes part in innate immunity by killing virus-infected cells?
Appeared in: RRB Nsg. Superintendent-21 July 2019 (Shift-2nd)
Explanation
- Natural Killer (NK) cells are a critical component of the innate immune system, providing a rapid first line of defense against viral infections and tumors.
- Unlike the adaptive immune system, NK cells do not require prior exposure or antigen presentation to recognize and kill target cells.
- NK cells identify virus-infected or cancerous cells by detecting the downregulation or absence of Major Histocompatibility Complex (MHC) class I molecules on the cell surface, a phenomenon known as 'missing-self' recognition.
- Upon activation, NK cells release cytotoxic granules containing perforin and granzymes, which induce apoptosis (programmed cell death) in the target cell.
Why Other Options Were Wrong
- Option A: Macrophages are primarily phagocytes that engulf and digest pathogens and cellular debris. While they are part of the innate immune system, their main role is not the direct killing of virus-infected host cells.
- Option B: T-cells, specifically cytotoxic T-lymphocytes (CTLs), do kill virus-infected cells, but they are a key component of the adaptive immune system, not the innate immune system. They require specific antigen presentation and prior activation.
- Option D: Neutrophils are phagocytic cells of the innate immune system that are most effective against extracellular bacteria and fungi. They are not the primary cell type for eliminating virus-infected host cells.
Related Visual
- Visual 1: Diagram - A flowchart illustrating the mechanism of NK cell activation. It shows an NK cell interacting with a healthy cell (with MHC-I, leading to inhibition) versus a virus-infected cell (without MHC-I, leading to activation and killing).
- Visual 2: Infographic - A comparison table of innate vs. adaptive immunity, highlighting the key cells (NK cells, Macrophages vs. T-cells, B-cells), response time (rapid vs. slow), and specificity (non-specific vs. highly specific).
Clinical Relevance
- Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Cellular components of the innate immune system and their specific functions as background academic context rather than a clinical decision trigger.
- A robust NK cell response is crucial for controlling viral infections like herpesviruses, influenza, and hepatitis. Patients with NK cell deficiencies (NKD) are highly susceptible to severe and recurrent viral illnesses.
- NK cells play a vital role in cancer immunosurveillance by identifying and eliminating malignant cells before they can form tumors. Many modern cancer immunotherapies aim to boost NK cell activity.
- What if? If a patient has a genetic defect leading to non-functional perforin, their NK cells (and cytotoxic T-cells) would be unable to effectively kill target cells. This condition, known as Familial Hemophagocytic Lymphohistiocytosis (FHL), leads to uncontrolled immune activation and severe, life-threatening inflammation in response to infections.
How to Approach the Question
- First, identify the key concepts in the question stem: 'innate immunity' and 'killing virus-infected cells'.
- Evaluate each option based on these two criteria.
- Consider Option A (Macrophages) and D (Neutrophils). Both are part of innate immunity, but their primary function is phagocytosis, mainly of extracellular pathogens, not killing infected host cells.
- Consider Option B (T-cells). While cytotoxic T-cells kill virus-infected cells, they belong to the adaptive immune system, which contradicts the 'innate immunity' requirement.
- Consider Option C (NK-cells). These cells are part of the innate immune system, and their specialized function is to recognize and kill virus-infected and tumor cells. This matches both criteria.
- Therefore, NK-cells are the only option that fits both the branch of immunity (innate) and the specific function (killing virus-infected cells).
Concept Tested & Keywords
- Concept Tested: Cellular components of the innate immune system and their specific functions.
- Stem keywords: innate immunity, killing virus-infected cells
- Lead-in keywords: Which cells
Question ID
QzYekXTF5G9po68oRvnR6x
Practise the full RRB Nsg. Superintendent-21 July 2019 (Shift-2nd)
Attempt every question from this paper in a timed mock, then review the full solution for each one.
More Immunity Questions
- Passive immunity against tetanus is obtained by the administration of:
- Vaccines and toxoids produce:
- A type of immunity that occurs when the vaccination of a portion of population provides protection to unprotected individuals is:
- For which of the following there is no vaccine available?
- The antigen that forms loose and cotton wooly clumps during agglutination is \ \ \ \ \ \
- The transfer of antibodies from mother's milk to the baby is called:
- The major class of immunoglobulin present in human serum is?
- Which of the following does NOT contribute to the functions of innate immunity?
- Which of the following involves the introduction of antibodies into the body from an animal or person already immune to the disease?
- Which of the following is NOT a type of vaccine?
More RRB Nsg. Superintendent-21 July 2019 (Shift-2nd) Questions
- The most common cause of embolism is ?
- Myopia is corrected by using?
- The normal human body temperature is maintained by& x20;
- \ \ \ \ \ \ denotes one who never completed a pregnancy to the stage of& x20;
- The process involved in the development of a mature ovum is called & x20;
- The larynx is closed during swallowing by: & x20;
- How are ECG changes presented in ischemia and myocardial infarction? & x20;
- What information the nurse should consider while collecting the history of a child with suspected rheumatic fever?& x20;
- The storage form of carbohydrates in animals is& x20;
- Paedophilia is a form of