B cell receptor (BCR)A Y-shaped antibody fixed in the membrane; it binds one antigen.
AntigenThe molecule or particle that the receptor recognizes and binds.
NucleusLarge and round, with only a thin rim of cytoplasm round it.
Cell membraneThe boundary of the cell; the receptors are anchored in it.
Activation 7
AntibodiesFree Y-shaped proteins that bind the antigen.
Plasma cellAn activated B cell that makes and releases antibodies.
Memory B cellA long-lasting B cell that answers faster the next time.
Helper T cellIt recognizes the displayed piece and signals the B cell.
Clonal expansionThe activated B cell divides into many identical copies.
MHC class IIThe holder that displays a piece of antigen to the T cell.
CytokinesSignal proteins the helper T cell releases to other cells.
How this list was compiled: Every name and detail line was checked on 2026-09-30 against the US National Institute of Allergy and Infectious Diseases, Immune Cells, https://www.niaid.nih.gov/research/immune-cells; MedlinePlus, Immune response, https://medlineplus.gov/ency/article/000821.htm; Kenhub, Lymphocytes, https://www.kenhub.com/en/library/anatomy/lymphocytes, and Plasma cells; and Wikipedia, B cell, B-cell receptor, Plasma cell, Memory B cell and T helper cell, text only. Hints and detail lines are in our own words. Licence: own work
The drawing: Drawn for this site on 2026-09-30 from plain geometry. Own original drawing; nothing traced or copied. Licence: own work
How it works
This B cell diagram has two views. The first is one resting cell and works as a B cell receptor diagram. The second is a B cell activation diagram, read from left to right.
Read the full guide
One B cell
A B cell is a lymphocyte, a kind of white blood cell, with a large round nucleus. B cell receptors stand on its membrane. Each receptor is an antibody fixed in place, and it binds one antigen.
From antigen to antibodies
A receptor catches an antigen. The B cell takes it in, breaks it up and shows a piece on an MHC class II molecule. A helper T cell that recognizes the piece releases cytokines. The B cell then divides, which is clonal expansion. Some daughter cells become plasma cells and release antibodies; others become memory B cells.
A plasma cell’s antibodies match the receptor of the B cell it came from.
A receptor is fixed in the membrane; an antibody is the same Y shape set free.
Questions and answers
What does a B cell do?
It makes antibodies. Its receptor recognizes one antigen; once the cell is activated it multiplies, and its daughter cells release antibodies against that antigen. B cells also show pieces of antigen to T cells.
What is the difference between a plasma cell and a memory B cell?
A plasma cell is an activated B cell that makes and releases antibodies. A memory B cell stays in the body afterward, so the same antigen gets a faster answer the next time.
How is a B cell different from a T cell?
Both are lymphocytes, a kind of white blood cell. B cells make antibodies and T cells do not. Helper T cells, for example, signal other immune cells with cytokines.
Is the second view a B cell differentiation diagram?
Yes. It shows an activated B cell dividing and its daughter cells becoming plasma cells and memory B cells. The earlier stages, in which a B cell develops in the bone marrow, are not drawn.