Q1. Source– CSIR NET Nov 20, Session II
Suresh was bitten by a poisonous snake and was immediately treated with anti-venom human immunoglobulin and was saved. A year later, he was bitten by the same type of snake a second time. Predict his response to the venom from the second bite from the following:
- He will be fully protected from the effects of the poison for the second time because he developed adaptive immunity after the first snake bite.
- He will be equally sensitive on the first encounter because there will be no recall of the first encounter.
- There are residual cells or anti-venom antibodies that were involved in the original/ first encounter. Hence, he will be protected.
- There will be memory cells made after the first encounter, hence he will be more sensitive.
Core concept: Active vs passive immunity
Active Immunity:
Protection is developed when the body’s own immune system produces antibodies and memory cells after exposure to an antigen (infection or vaccination). It takes time to develop, but it provides long-term protection due to immunological memory.
Passive Immunity:
Protection obtained by receiving pre-formed antibodies from an external source (e.g., antivenom or immunoglobulin). It provides immediate but short-term protection and does not generate memory cells.
Statement analysis
A.
He was given anti-venom in the form of antibodies (immunoglobulin). Since these antibodies were not produced by his own immune system, immunological memory will not develop. Therefore, this option is incorrect.
B.
This option is correct. Because the first exposure involved passive immunization, the immune system did not generate memory cells, so there will be no recall response during the second snake bite. Hence, he will be equally sensitive as during the first encounter.
C.
Passive immunity does not produce memory B cells or long-term antibody production. The administered antibodies are eventually degraded and cleared from circulation, so no residual protective cells or antibodies remain. Therefore, this option is incorrect.
D.
Memory cells are not formed during passive immunization, so the body will not develop increased sensitivity or a secondary immune response. Hence, this option is incorrect.
Correct answer: Option B
Q2. Source: ICMR JRF 2020
Phagocytosis enhanced by coating the surface of the antigen is called:
- Opsonization
- Chemotaxis
- Decoding
- Compliment Fixation
Statement Analysis
A. Opsonization
Opsonization is the coating of a pathogen with molecules such as antibodies (IgG) or complement proteins (C3b) that enhance its recognition and ingestion by phagocytes like macrophages and neutrophils. This process significantly increases the efficiency of phagocytosis.
B. Chemotaxis
Chemotaxis is the directed movement of immune cells toward a chemical signal, usually toward sites of infection or inflammation. It helps phagocytes reach pathogens but does not enhance phagocytosis by coating the antigen.
C. Decoding
Decoding in immunology generally refers to analyzing or interpreting immune responses, often using computational or molecular techniques. It is not a mechanism involved in phagocytosis.
D. Complement Fixation
Complement fixation is a serological diagnostic test used to detect the presence of specific antibodies or antigens based on complement activation. It does not refer to coating pathogens to enhance phagocytosis.
Exam insights
Be clear with core immunology definitions. Direct questions often test quick recall of terminology under time pressure!