Types of Immunity and Defense Mechanisms — NEET Biology
📚 Practice ConceptImmunity is of two types: (i) Innate immunity and (ii) Acquired immunity.
Which of the following statements about the body's innate immune barriers are NOT correct? S1: The skin provides a physical barrier, while the mucous coating in the respiratory tract acts as a cytokine barrier. S2: Acid in the stomach and saliva in the mouth are examples of physiological barriers that prevent microbial growth. S3: Phagocytic leukocytes like neutrophils and macrophages constitute a part of the cellular barriers of innate immunity. S4: Interferons secreted by virus-infected cells are crucial components of the cytokine barrier, protecting non-infected cells. S5: Natural Killer (NK) cells, a type of lymphocyte, are primarily involved in the specific recognition and destruction of pathogens, making them part of acquired immunity.
View solution & NCERT explanation
Correct answer: B — S1 and S5 only
This question examines the different types and components of innate immunity barriers. S1: The skin is a physical barrier, and mucous coating is also a physical barrier, trapping microbes. Cytokine barriers involve proteins like interferons. Therefore, stating mucous coating as a cytokine barrier is NOT correct. S2: Acid in the stomach, saliva in the mouth, and tears from eyes are all examples of physiological barriers that prevent microbial growth. This statement is correct. S3: Polymorpho-nuclear leukocytes (PMNL-neutrophils), monocytes, and macrophages are phagocytic leukocytes that constitute the cellular barriers of innate immunity. This statement is correct. S4: Virus-infected cells secrete interferons, which act as cytokine barriers, protecting non-infected cells from further viral infection. This statement is correct. S5: Natural Killer (NK) cells are a type of lymphocyte and part of the cellular barrier of *innate* immunity. They do not involve specific recognition associated with acquired immunity. Therefore, classifying them as part of acquired immunity in this context is NOT correct. Thus, statements S1 and S5 are NOT correct.
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.