12/01/25 B cells

B Cell Receptors

Neuroglobulins on B cells that recognize and bind antigens.

MHC class II

A receptor on B cells that presents processed antigens to T helper cells (CD4+ T cells).

T helper cell (CD4+ T cell)

A type of immune cell that binds to antigen presented by a B cell, leading to B cell activation and strengthened by the CD4 molecule.

Clonal Expansion

The process where activated B cells increase in size (nucleotide expansion due to DNA replication) and proliferate, producing many B cells that target the same specific antigen.

Clonal selection

The process where a B or T cell that recognizes a specific antigen is activated to divide rapidly, producing many identical effector cells and memory cells.

Memory B Cells

B cells produced during clonal expansion that retain receptors for quick recognition of the initiating antigen during future encounters.

Plasma Cells

Specialized B cells produced during clonal expansion that are responsible for high-rate antibody production.

Antibody (Immunoglobulin)

A protein consisting of four polypeptide chains (two heavy and two light) with antigen binding sites and a crystallizable fragment (Fc) that communicates with the immune system.

FAB region (antigen-binding fragments)

The part of an antibody that is crucial for recognizing and binding to antigens.

Fc region (crystallizable fragment)

The lower part of an antibody that communicates the signal of the bound antigen to the immune system and can bind to different immune cells to induce responses.

Cytokines

Cytokines are special proteins that act as messengers between cells. They are like signal molecules that tell other cells what to do, influencing a wide range of body activities. For instance, they help coordinate immune responses to fight infections, regulate inflammation (like swelling from an injury), and even guide the formation of new blood cells.

Activation of Complement

A mechanism where antibodies activate the complement system, leading to the formation of pores in pathogens and their destruction.

Opsonization

A mechanism where antibodies adhere to pathogens, marking them for engulfment by phagocytic cells like macrophages.

Blocking Viral Receptors

A mechanism where antibodies prevent viruses from binding to host cell receptors, thereby inhibiting infection.

Agglutination

A mechanism where antibodies bind multiple cells together, making them more easily recognized as foreign by the immune system.

Precipitation

A mechanism where antibodies bind to smaller molecules, forming immune complexes that facilitate their elimination from the body.

Neutralization of Toxins

A mechanism where antibodies bind to and neutralize toxins, preventing them from interacting with host tissues.

Immunoglobulin M (IgM)

A pentamer-structured antibody, it is the first antibody produced in response to infections and is effective in activating complement.

Immunoglobulin E (IgE)

A monomer-structured antibody crucial for allergic reactions and mediating responses against parasitic infections by binding to mast cells and eosinophils.

Latent Period (B Cell Response)

The initial period after first exposure to an antigen (approximately two weeks) during which no antibodies are detectable in the blood.

Primary Response

The immune response following initial antigen exposure, characterized by an initial peak of IgM, closely followed by IgG production.

Secondary Response (Anamnestic Response)

A more rapid and robust immune response upon subsequent exposure to the same antigen, enabled by memory B cells and resulting in a higher antibody titer.