Innate vs Acquired & Active vs Passive Immunity — NEET Biology

Correct answer: C — S1 and S3

This question tests the understanding of active vs. passive immunity, cell-mediated immunity, and the roles of specific antibodies, focusing on identifying incorrect statements. S1 is NOT correct: The description provided, where preformed antibodies or antitoxins are directly injected, defines passive immunity, not active immunity. Active immunity is when a host produces its own antibodies. The NCERT states, 'When ready-made antibodies are directly given to protect the body against foreign agents, it is called passive immunity.' S2 is correct: Cell-mediated immunity (CMI) is indeed mediated by T-lymphocytes. While T-cells do not produce antibodies themselves, they assist B-cells in antibody production. The NCERT confirms, 'The T-lymphocytes mediate CMI. The T-cells themselves do not secrete antibodies but help B cells to produce them.' S3 is NOT correct: While IgA antibodies are found in colostrum and mucosal surfaces, they are a component of acquired (adaptive) immunity, not innate immunity. Innate immunity is non-specific and present at birth, involving physical, physiological, cellular, and cytokine barriers. The NCERT lists IgA as an antibody, which is part of acquired immunity (Section 7.2.2) and describes innate immunity barriers in Section 7.2.1 without mentioning IgA. S4 is correct: This statement accurately describes allergy, where IgE antibodies bind to mast cells, leading to histamine release. The NCERT states, 'The antibodies produced to these are of IgE type. ... Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.' S5 is correct: Vaccination relies on the immune system's memory to generate a quick and intense secondary response upon subsequent exposure to a pathogen. The NCERT states, 'The principle of immunisation or vaccination is based on the property of ‘memory’ of the immune system. ... The vaccines also generate memory – B and T-cells...' Therefore, S1 and S3 are NOT correct. This question integrates concepts of active/passive immunity, cell-mediated immunity, and the specific functions and classification of antibodies within the immune system.