humoral immune response
DESCRIPTION
Humoral Immune ResponseTRANSCRIPT
Results in production of proteins called “immunoglobulins” or “antibodies”.
Body exposed to “foreign” material termed “antigen” which may be harmful to body: virus, bacteria, etc.
Antigen has bypassed other protective mechanisms, ie, first and second line of defense.
Primary immune response◦ Latent period◦ Gradual rise in antibody production taking days to
weeks◦ Plateau reached ◦ Antibody level declines
Antibody production◦ Initial antibody produced in IgM◦ Lasts 10-12 days◦ Followed by production of IgG◦ Lasts 4-5 days◦ Without continued antigenic challenge antibody
levels drop off, although IgG may continue to be produced.
a lag phase where no antibody is detected a log phase in which the antibody titer rises
logarithmically a plateau phase during which the antibody titer
stabilizes a phase (decline) during which the antibody is
cleared or catabilized
Second exposure to SAME antigen. Memory cells are a beautiful thing. Recognition of antigen is immediate. Results in immediate production of
protective antibody, mainly IgG but may see some IgM
APC
APC
APC
TH
TH
B
APC
The Microbial antigen is ingested by an APC and partially digested. Fragments from microbe bind with the MHC II to form a MHC II /Ag complex on the surface of the APC
APC
APCTH
A Helper T cell, specific for the presented antigen, binds to the MHC II/Ag complex
Memory cells do not react right away but are held in reserve for later infections. The secondary response that is carried out by memory cells is different in 3 ways.
Memory cells produce antibodies that bind with greater affinity to their antigens than the antibodies produced in the initial response.
The response time is much faster than the primary response
A greater number of antibodies are produced.
Virgin lymphocyte pool Virgin lymphocyte pool
PRIMARY RESPONSE PRIMARY RESPONSE
SECONDARY SECONDARY RESPONSERESPONSE
effector cells effector cells memory cell pool memory cell pool
effector cells effector cells memory cell pool memory cell pool
antibodantibody titery titer
time time
IgGIgG IgMIgM
Time course Antibody titer Antibody class Antibody affinity
Antibodies function in 6 ways to protect the body◦ Agglutination: Enhances
phagocytosis and reduces number of infectious units to be dealt with
◦ Opsonization: Coating antigen with antibody enhances phagocytosis
◦ Neutralization: blocks adhesion of bacteria and viruses to mucosa. Also blocks active site of toxin
Activation of complement
Increases inflammation through the byproducts of the complement system (C5a and C3a)
Antibody dependant cell mediated cytotoxicity: Antibodies attached to target cell cause destruction by non specific immune system cells.
Antigenic modulation is distinct from antigen shaving in which the antigen/antibody complex is skimmed from the surface of the malignant B cell by macrophages, usually in the spleen. With antigenic modulation the antibody is internali
zed by the malignant B cells. Note that both these mechanisms consume the monoclonal antibody and may account for the more rapid than expected clearance of antibody from the circulation.