What is the correct sequence of events for activation of a b cell by a t-dependent antigen? (1) the b cell binds to a cytokine and then interacts with the th cell. (2) this causes the b cell to bind the antigen, and then the b cell is activated. (1) immunoglobulin receptors on the b cell recognize and bind the antigen. (2) an antigen fragment in complex with mhc class 2 is displayed on the b cell's surface. (3) the mhc-antigen complex binds a receptor on a th cell. (4) the th cell secretes cytokines that activate the b cell. (1) identical repeating subunits on the antigen bind to many of the antibodies on the surface of the b cell. (2) this activates the b cell. (1) the t cells bind to an antibody on the b cell. (2) the t cell secretes cytokines. (3) the b cell binds the antigen. (4) the b cell is activated by binding to the antigen.

Antigens that activate B-cells with the help of T-cells are called as T-cells dependent antigens. They are called as such because they are not able to induce a humoral response in organisms that lack T-cells. B-cells response to these antigens take many days, thought antibodies generated are more versatile and have a higher affinity than those generated from T-cell independent activation.

So, the steps for activation of a B cell by a T-dependent antigen are:

(1) Immunoglobulin receptors on the B cell recognize and bind the antigen.

(2) An antigen fragment in complex with MHC class 2 is displayed on the B cell's surface.

(3) The MHC-antigen complex binds a receptor on a TH cell.

(4) The TH cell secretes cytokines that activate the B cell.

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