(a) Define Humoral immune response. [1]
(b) Name any two types of antibodies found to give humoral immune response in humans. [1]
(a) Define Humoral immune response. [1]
(b) Name any two types of antibodies found to give humoral immune response in humans. [1]
Official answer
(a) Humoral immune response:
The type of immunity in which B-lymphocytes produce antibodies that circulate in the body fluids (blood, lymph) and defend the body against antigens. It is also called antibody-mediated immunity (AMIS) because it is carried out by antibodies present in the 'humors' (body fluids).
(b) Two types of antibodies (any two):
- IgG
- IgA
- IgM
- IgE
- IgD
(Naming any two, e.g. IgG and IgM, earns the mark.)
Marking scheme
- 1.1 mark (a): defining humoral response as antibody-mediated immunity by B-lymphocytes acting through body fluids (antibody-mediated / AMIS).
- 2.1 mark (b): naming any two antibody classes correctly (IgG, IgA, IgM, IgE, IgD) — ½ mark each.
Hint
Humoral = antibodies in body fluids from B-cells; the antibody classes all start with 'Ig'.
Quick oral answer
The humoral immune response is antibody-mediated immunity in which B-lymphocytes and plasma cells release antibodies into the body fluids to fight antigens; two antibody types active in humans are IgG and IgM.
Common mistakes
- 1.Attributing the humoral response to T-lymphocytes; it is mediated by antibodies from B-cells (T-cells drive cell-mediated immunity).
- 2.Listing antibody chains (heavy/light) instead of antibody classes (IgG, IgA, IgM, IgE, IgD) as asked in part (b).
- 3.Writing vague definitions like 'immunity by blood' without mentioning antibodies or B-cells.
Analysis and explanation
Concept — Two arms of specific immunity:
Acquired (specific) immunity has two components:
- Humoral immune response (AMIS): mediated by antibodies secreted by B-cells / plasma cells, acting in body fluids.
- Cell-mediated immune response (CMI): mediated by T-lymphocytes, which act against infected cells, grafts, etc.
Why it is called 'humoral':
The term comes from 'humors', the old word for body fluids, because the antibodies float freely in blood and lymph rather than being fixed to cells.
Antibody structure link:
Each antibody is a protein with four peptide chains (two heavy + two light), written as , and the human classes are IgA, IgD, IgE, IgG and IgM.
Exam trap:
- Do not write T-cell responses here — antibodies come from B-cells.
- The question asks for types of antibodies (Ig classes), not the parts of an antibody. Writing 'heavy and light chains' will not score.
Interesting facts
The five human antibody classes are IgA, IgD, IgE, IgG and IgM; IgG can cross the placenta to give a newborn passive natural immunity.
IgA is secreted in colostrum, the first milk, giving breastfed infants passive protection against gut infections.
Each antibody molecule is Y-shaped with two identical antigen-binding sites, allowing it to neutralise or tag antigens for destruction.
Question details
Q17 of 37 questions
- Board
- CBSE
- Class
- Class 12
- Subject
- Biology
- Year
- 2026
- Section
- Section B
- Marks
- 2
- Type
- Very Short Answer
- Chapter
- Human Health and Disease
- Topic
- Humoral Immune Response
- Bloom's level
- remember
- Syllabus topic
- Unit VII: Human Health and Disease — Immunity: Humoral (Antibody-Mediated) Immune Response
- Author
- CBSE
- Reviewed by
- Padhantu Academic Team
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Frequently asked questions
What is the difference between humoral and cell-mediated immunity?
Humoral immunity is carried out by antibodies produced by B-lymphocytes that act in body fluids against free antigens, while cell-mediated immunity is carried out by T-lymphocytes that act directly against infected cells, tumour cells and grafts.
How many types of antibodies are there in humans?
There are five classes of antibodies (immunoglobulins) in humans: IgA, IgD, IgE, IgG and IgM. Any two of these are acceptable for the second part of the question.