Which of the following statements are correct?
I. Allergy refers to an exaggerated immune response to specific antigens present in the environment.
II. The antibodies produced in response to allergens are of IgG type.
III. For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens, and the reactions are studied.
IV. A subsequent encounter with the same pathogen elicits a highly intensified secondary or anamnestic response.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → I, III and IV
I. Allergy refers to an exaggerated immune response to specific antigens present in the environment. — True. Allergy is the exaggerated response of the immune system to certain antigens around us, such as mites in dust, pollens and animal dander. Such substances are called allergens.
II. The antibodies produced in response to allergens are of IgG type. — False. The antibodies made against allergens are of the IgE type, not IgG. Allergy is due to the release of chemicals like histamine and serotonin from the mast cells.
III. For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens, and the reactions are studied. — True. The allergen that produces a reaction in such a test is the cause of the allergy.
IV. A subsequent encounter with the same pathogen elicits a highly intensified secondary or anamnestic response. — True. Acquired immunity is marked by memory. The first encounter gives a weak primary response, and the body remembers it, so a later encounter gives a much stronger secondary response.
NCERT Extract:
Allergies – “… The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The substances to which such an immune response is produced are called allergens. The antibodies produced to these are of IgE type. Common examples of allergens are mites in dust, pollens, animal dander, etc. Symptoms of allergic reactions include sneezing, watery eyes, running nose and difficulty in breathing. Allergy is due to the release of chemicals like histamine and serotonin from the mast cells. For determining the cause of allergy, the patient is exposed to or injected with very small doses of possible allergens, and the reactions studied.”
Acquired Immunity – “Acquired immunity, on the other hand is pathogen specific. It is characterised by memory. This means when our body encounters a pathogen for the first time it produces a response called primary response which is of low intensity. Subsequent encounter with the same pathogen elicits a highly intensified secondary or anamnestic response.”