When antigens are introduced in the body through vaccination antibodies are produced to fight off infection
By only B cells
Antibodies are made by B cells alone — option 2.
The division of labour in immunity. Both kinds of lymphocyte arise from stem cells in the bone marrow, but they mature differently and do different work :
| B lymphocyte | T lymphocyte | |
|---|---|---|
| Matures in | Bone marrow | Thymus |
| Type of immunity | Humoral — antibody-mediated | Cell-mediated |
| What it does | On meeting its antigen it becomes a plasma cell and secretes antibodies into the blood | Kills infected cells directly (cytotoxic T), or helps and regulates other cells (helper and regulatory T) |
| Acts against | Free bacteria, toxins and viruses in the blood and body fluids | Virus-infected cells, cancer cells, transplanted tissue |
Why option 1 is so tempting. Helper T cells are essential to a good antibody response: they recognise the antigen presented to them and release signals that drive the B cell to divide and to switch antibody class. So T cells are indispensable to the process. But they do not themselves secrete antibody — that is done exclusively by the plasma cells derived from B lymphocytes. The question asks who produces the antibodies, and only one cell type does.
How vaccination works. A vaccine introduces the antigen — a killed or weakened organism, a purified protein, or the mRNA instructions to make one — without the disease. The immune system responds, and, crucially, leaves behind memory B and T cells. On a real infection the response is then far faster and larger, and the disease is prevented. This is active immunity, and it is lasting; giving ready-made antibodies, as in an anti-tetanus or anti-snake-venom serum, gives passive immunity, which acts at once but does not last.
Antibodies are Y-shaped proteins, the immunoglobulins, of five classes — IgG, IgM, IgA, IgE and IgD. IgG crosses the placenta and protects the newborn; IgA is in milk, saliva and tears; IgE mediates allergy.
Hence, the answer is By only B cells.
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