Your body makes five types of antibodies (immunoglobulins): IgG, IgA, IgM, IgE and IgD. IgG is the most common in blood, IgA is found in colostrum and protects the newborn's gut, IgM is the largest and is made first in an infection, and IgE causes allergy. Memory hook: "GAMED" - G, A, M, E, D are the five types.
The five antibody types and their key NEET facts. All share the same H2L2 structure but differ in location and job: IgG (blood, placenta), IgA (colostrum), IgM (largest, made first), IgE (allergy), IgD (B-cell surface).
Your doubts, answered
Which antibody is present in colostrum (mother's first milk)?
IgA. NCERT says the yellowish colostrum secreted in the first days of lactation has abundant antibodies (IgA) to protect the newborn baby. Because ready-made antibodies pass from mother to baby, this is passive immunity. This is asked again and again in NEET (2019, ReNEET 2026), so lock it: colostrum = IgA.
Which is the largest antibody?
IgM is the largest antibody. It is a pentamer (five units joined together), so it is much bigger than the other types. It is also the first antibody made when a pathogen enters the body for the first time (primary response). Memory: M = Massive and Made first.
Which antibody is the most abundant in the blood?
IgG is the most abundant antibody in blood and body fluids. It is the main antibody of the secondary response and it can cross the placenta to give the baby natural passive immunity before birth. So: colostrum after birth = IgA, across the placenta before birth = IgG.
Which antibody causes allergy?
IgE causes allergic reactions. In an allergy, IgE binds to mast cells and triggers the release of histamine, which gives symptoms like sneezing, runny nose and watery eyes. Memory: E = allErgy. Anti-histamines are used to reduce these symptoms.
What is the difference between IgG and IgA?
IgG is the most abundant antibody in blood and crosses the placenta (before birth). IgA is found in secretions like colostrum, saliva, tears and mucus, and protects body surfaces such as the gut and airways. In NEET a common trap is: colostrum has IgA, NOT IgG.
Which antibody is produced first in a new infection?
IgM is produced first. When a pathogen is met for the first time, the primary immune response makes IgM first. Later, and in the faster secondary response, IgG becomes the main antibody. So first = IgM, later/most = IgG.
⚠️ The NEET trap ✗ Colostrum protects the newborn because it contains IgG (or contains cells like macrophages / natural killer cells). ✓ Colostrum is rich in IgA, which protects the newborn's gut. This is passive immunity because ready-made antibodies are given to the baby. 🧠 Before birth = IgG crosses the placenta. After birth = IgA in colostrum. NEET picks the door based on timing, so read whether the question says placenta or colostrum.
Real NEET questions
NEET 2019
Colostrum the yellowish fluid, secreted by mother during the initial days of lactation is very essential to impart immunity to the new born infants because it contains:
A · Natural killer cells
B · Monocytes
C · Macrophages
D · Immunoglobulin A ✓
Solution: NCERT states that colostrum, secreted during the first days of lactation, has abundant antibodies (IgA) to protect the infant. Because ready-made antibodies pass to the baby, this is passive immunity. Natural killer cells, monocytes and macrophages are cells of innate immunity, not the antibody that colostrum provides.
ReNEET 2026
Colostrum, secreted by the mother during the initial days of lactation, is abundant in ________.
A · IgG
B · IgM
C · IgA ✓
D · IgD
Solution: Colostrum is rich in IgA, which protects the newborn's gut (a form of passive immunity). IgG, by contrast, crosses the placenta to give natural passive immunity before birth, so it is the trap option here.
NEET 2025
Identify the statement that is NOT correct.
A · Antigen binding site is located at C-terminal region of antibody molecules. ✓
B · Constant region of heavy and light chains are located at C-terminus of antibody molecules.
C · Each antibody has two light and two heavy chains.
D · The heavy and light chains are held together by disulfide bonds.
Solution: The antigen-binding site lies in the VARIABLE region at the N-terminal ends of the chains, not the C-terminal, so statement A is incorrect. Every antibody type (IgG, IgA, IgM, IgE, IgD) shares the same basic H2L2 structure: two heavy and two light chains held by disulfide bonds, with constant regions at the C-terminus.
Solved Human Health and Diseases NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
There are five types of antibodies (immunoglobulins): IgG, IgA, IgM, IgE and IgD. Remember them with the word GAMED.
What is the memory trick for the antibody types?
Use GAMED for the five types (G, A, M, E, D). For their jobs: G = most in blood + crosses placenta, A = colostrum + secretions, M = Massive + Made first, E = allErgy, D = D (least understood, on B-cell surface).
Do all antibodies have the same structure?
Yes, all five share the same basic H2L2 structure - two heavy chains and two light chains held by disulfide bonds. They differ mainly in the type of heavy chain and in how many units join (for example, IgM is a pentamer).
Which antibody crosses the placenta?
IgG crosses the placenta, giving the baby natural passive immunity before birth. After birth, the baby gets IgA through colostrum.
Why is IgA important for NEET?
IgA is the single most-tested antibody in NEET because of colostrum. NCERT directly says colostrum has abundant IgA, and this exact fact has appeared in multiple years (2019 and ReNEET 2026).
