Phagocytosis is considered as which line of defense against infection?

HPSSC Staff Nurse - 2021

Applied Physiology

Easy

Appeared in: HPSSC Staff Nurse - 2021

Explanation

Phagocytosis is the process where cells like neutrophils and macrophages engulf and digest pathogens.
This process is a fundamental part of the innate immune system, which provides a rapid, non-specific response to infection.
The innate immune system's internal mechanisms, including phagocytosis, inflammation, and fever, constitute the body's second line of defense.
It is activated when pathogens get past the first line of defense (physical and chemical barriers).

Option A: The first line of defense consists of physical and chemical barriers like the skin, mucous membranes, and stomach acid, which prevent pathogens from entering the body. Phagocytosis is a cellular process that occurs after these barriers have been breached.
Option C: The third line of defense is the adaptive (or acquired) immune system. It is a specific response involving lymphocytes (T-cells and B-cells) and antibody production, which provides long-lasting immunity. Phagocytosis is part of the non-specific innate response.
Option D: The concept of a 'fourth line of defense' is not a recognized or standard classification in immunology. The immune system is traditionally described as having three lines of defense.

Clinical Relevance

Nursing practice connection: Knowing Lines of defense in the immune system helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
A low count of phagocytic cells, particularly neutrophils (a condition called neutropenia), severely compromises the second line of defense, placing patients at a very high risk for bacterial and fungal infections.
Nurses caring for neutropenic patients (e.g., those on chemotherapy) must implement strict infection control measures, known as neutropenic precautions, which include meticulous hand hygiene, avoiding fresh flowers or raw foods, and monitoring for early signs of infection like fever.
What if? If a patient has extensive burns, their first line of defense is compromised. This breach allows pathogens direct access to the tissues, immediately overwhelming the second line of defense (phagocytes) and increasing the risk of systemic infection (sepsis).

How to Approach the Question

First, identify the core concept in the question, which is 'phagocytosis'.
Recall the definition of phagocytosis: the process of cells engulfing pathogens.
Next, recall the standard model of the body's defense systems, which is organized into three 'lines'.
Categorize where phagocytosis fits. The first line is barriers (skin). The third line is specific immunity (antibodies, T/B cells). The second line is the innate cellular response that happens when barriers are breached.
Since phagocytosis is a key part of this innate cellular response, it belongs to the second line of defense.
Select the option that matches this conclusion.

Concept Tested & Keywords

qi_OUoKobot7aRoDcSplE

E6 Medicine Davidson Principles Practice 24e p. 83-85

E6 PATHOLOGY QUICK REVIEWBased on Harsh Mohan Textbook of PATHOLOGY p. 34-36