Humoral Immune Response: Definition and Summary of Steps involved

Definition: Host defense mechanisms that are mediated by antibodies produced by plasma cells of B cells.
It protects against extracellular bacteria and foreign macromolecules.

Diagram: Steps in Humoral Immune Response

Step 1:

B cell activation=Antigen binding to Naïve B cell receptor

B cell possess B cell receptor or BCR with a single specificity. A naive B cell is the one which hasn't encountered an antigen before. When an epitope of an antigen binds to the B cell receptor, that particular B cell gets activated.

Step 2:

Clonal selection: Division of that activated B cell

This activated B cell is selected to divide forming many copies of that cell. That particular clone of B cell is selected to divide and is called as clonal selection.

Step 3:

Differentiation: Plasma cells and memory B cells

Later this B cells differentiate to form plasma cells or effecter cells and and memory B cells

Step 4:

Plasma cells produce antibodies that binds to the antigen and ensures it clearance from the system.

Memory B cells are meant for immunologic memory or secondary immune response. When the same antigen comes for the second time, these memory B cells will recognize it quickly and induce a heightened immune response. This will clear out the pathogen from the system soon.

There is one more pathway in humoral immune response which is mediated by T helper cells.

For videos

• Pathway 1: Steps in Humoral immune response, B cell mediated antibody production
• Pathway 2: Steps in Humoral immune response, T helper cell - B cell mediated antibody production or B cell as antigen presenting cell