Humoral Immune Response
Immunology _ Antibody Mediated Immune Response
The antibody-mediated, or humoral, immune response involves B cells that
produce antibodies specific to antigens circulating in the blood.
B cells develop in the bone marrow, travel to the spleen, and mature into cells
specific for one antigen.
Antibody-mediated immunity begins when an antigen binds to an antigen-
presenting cell, or APC. An APC may be a macrophage, dendritic cell, or B cell.
The antigen is taken in by the APC and broken down into peptide fragments,
which combine with class II major histocompatibility complex, or MHC II self-
antigens, and move to the APC's
plasma membrane. Helper T cells recognize the antigen-MHC complex and
become activated.
The activated helper T cell then binds to and activates a matching B cell. Once
attached, it secretes cytokines, such as interleukin-2, to stimulate the B cell to
undergo clonal selection. During clonal selection, the B cell multiplies to form
plasma cells and memory B cells.
The plasma cells produce millions of antibodies over the next four or five days, in
a process enhanced by interleukin-4 and 6 from helper T cells.
The memory cells remain in the body, ready for future immunity.
If we look closely at the structure of an antibody, we see that it consists of four
chains, two heavy, or H-chains, and two light, or L-chains.
Each of the chains contains two regions,
a variable region that recognizes and attaches to an antigen, and a constant
region that is responsible for the type of antigen-antibody reaction.
The constant region of the H-chain identifies the antibody as belonging to one of
five classes IgG, IgA, IgM, IgD, or IgE.
Antibodies circulate through the body and bind to specific antigen-binding sites
on the surface of invading microbes, much as a lock matches a specific key. The
antigen-antibody binding also triggers the complement system. The binding of
an antibody neutralizes many antigens. It may also immobilize bacteria by
binding to their flagella, or agglutinate and precipitate
antigens by binding several together.
Immunology _ Antibody Mediated Immune Response
The antibody-mediated, or humoral, immune response involves B cells that
produce antibodies specific to antigens circulating in the blood.
B cells develop in the bone marrow, travel to the spleen, and mature into cells
specific for one antigen.
Antibody-mediated immunity begins when an antigen binds to an antigen-
presenting cell, or APC. An APC may be a macrophage, dendritic cell, or B cell.
The antigen is taken in by the APC and broken down into peptide fragments,
which combine with class II major histocompatibility complex, or MHC II self-
antigens, and move to the APC's
plasma membrane. Helper T cells recognize the antigen-MHC complex and
become activated.
The activated helper T cell then binds to and activates a matching B cell. Once
attached, it secretes cytokines, such as interleukin-2, to stimulate the B cell to
undergo clonal selection. During clonal selection, the B cell multiplies to form
plasma cells and memory B cells.
The plasma cells produce millions of antibodies over the next four or five days, in
a process enhanced by interleukin-4 and 6 from helper T cells.
The memory cells remain in the body, ready for future immunity.
If we look closely at the structure of an antibody, we see that it consists of four
chains, two heavy, or H-chains, and two light, or L-chains.
Each of the chains contains two regions,
a variable region that recognizes and attaches to an antigen, and a constant
region that is responsible for the type of antigen-antibody reaction.
The constant region of the H-chain identifies the antibody as belonging to one of
five classes IgG, IgA, IgM, IgD, or IgE.
Antibodies circulate through the body and bind to specific antigen-binding sites
on the surface of invading microbes, much as a lock matches a specific key. The
antigen-antibody binding also triggers the complement system. The binding of
an antibody neutralizes many antigens. It may also immobilize bacteria by
binding to their flagella, or agglutinate and precipitate
antigens by binding several together.
