Cell Mediated Immune Response Diagram

All 15 parts on the diagram

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Two arms 8

Cytotoxic T cell It kills infected cells. Also called a killer T cell or CD8 T cell.
Helper T cell It gives off cytokines that help B cells and other T cells.
Antigen-presenting cell It shows a piece of antigen to a T cell. Dendritic cells are one kind.
Cytokines Proteins made by cells that change what other cells do.
B cell It carries receptors for one antigen. Activated, it gives rise to plasma cells.
Plasma cell It makes and secretes antibodies. It comes from a B cell.
Antibodies Proteins that plasma cells secrete. Each binds one specific antigen.
Memory T cell A long-lived T cell, ready to respond to the same antigen again.

Close up 7

Target cell (infected cell) The cell under attack, here one infected by a virus. It dies by apoptosis.
MHC class I molecule It carries a peptide from inside the cell to the cell surface.
Antigen (peptide) A short piece of protein from inside the target cell.
T cell receptor (TCR) It binds the piece of antigen held in the MHC molecule.
CD8 A co-receptor on the T cell. It binds the side of the MHC class I molecule.
Perforin A protein that makes pores in the target cell's membrane.
Granzymes Enzymes that enter through the pores and trigger apoptosis.

How this list was compiled: Every name and what each part does read on 2026-10-01 and kept only where both of these have it. (1) Wikipedia, text only: Cytotoxic T cell, Cell-mediated immunity, Humoral immunity and Perforin-1 (perforin forms pores on the target cell), https://en.wikipedia.org/wiki/Cytotoxic_T_cell , https://en.wikipedia.org/wiki/Cell-mediated_immunity , https://en.wikipedia.org/wiki/Humoral_immunity : the killer T cell and its other names, the T-cell receptor on a peptide held by a class I MHC molecule, CD8 on the side of that molecule, perforin, granzymes and apoptosis, memory T cells, antigen-presenting cells, helper T cells and cytokines, and antibodies secreted by plasma cells that come from B cells. (2) Parham, The Immune System, read as passages found by the Internet Archive's full-text search, https://archive.org/details/immunesystem00pete : cytotoxic CD8 T cells and MHC class I, the CD8 co-receptor, perforin making pores in the target cell membrane through which granzymes enter, apoptosis of the target cell, cytokines, helper T cells, antigen-presenting cells, plasma cells secreting antibodies, long-lived memory T cells. Hints and detail lines are in our own words. Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain geometry. Own work; nothing traced or copied. Licence: own work

How it works

The first drawing is a humoral and cell mediated immunity diagram: a helper T cell sends cytokines to a B cell and to a cytotoxic T cell. The second is a killer T cell diagram, close up on its target.

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Two arms

An antigen-presenting cell shows antigen to a helper T cell, which gives off cytokines. In the humoral arm a B cell gives rise to a plasma cell that secretes antibodies. In the cell-mediated arm a cytotoxic T cell kills infected cells, and memory T cells stay behind.

Close up

The T cell receptor binds a peptide held in an MHC class I molecule, and CD8 binds the side of that molecule. Perforin makes pores in the target cell's membrane. Granzymes pass through them, and the cell dies by apoptosis.

Cytotoxic T cell, killer T cell and CD8 T cell are three names for one cell.

Questions and answers

What is the cell mediated immune response?

The part of the adaptive immune response that works through cells and not through antibodies. Cytotoxic T cells find infected cells and kill them, helped by cytokines from helper T cells.

What is the difference between humoral and cell mediated immunity?

Humoral immunity works through antibodies, which plasma cells secrete into the body fluids. Cell mediated immunity works through cells, chiefly cytotoxic T cells that kill infected cells. Helper T cells support both arms.

How does a cytotoxic T cell kill a target cell?

Its receptor recognizes a peptide held in an MHC class I molecule on the target cell. The T cell then releases perforin, which makes pores in the target cell's membrane, and granzymes, which enter through the pores and trigger apoptosis.

Is a killer T cell the same as a cytotoxic T cell?

Yes. Killer T cell, cytotoxic T cell, cytotoxic T lymphocyte and CD8 T cell are names for the same cell. The last name comes from CD8, a glycoprotein on its surface.