Antibody Mediated Immunity
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What is Antibody Mediated Immunity or Humoral Immunity?
What are the 7 Steps of Antigen-Antibody Interactions?
It involves the antigen-antibody interactions to neutralize, eliminate or destroy foreign proteins.
The body learns to make enough of any specific antibody to provide long-lasting immunity and protection against specific organisms or toxins.
- The Seven Steps are:
- Antigen Recognition
- Lymphocyte Sensitization
- Antibody Production and Release
- Antigen-antibody binding
- Antibody-Binding reactions
- Sustained immunity or memory
What are the effects of antibody mediated immunity?
- increased vascular permeability
- chemotaxis - is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment
alterations in immune response
over reaction -->hypersensitivity --> allergies -->anaphylaxis
- Self reaction --> autoimmune diseases
- Under reaction --> immunodeficiency
- HIV --> AIDS (CD4 <200)
- Reduced T-helpers --> reduced B - Cell Function
Where are antibodies produced? What does it do?
- Antibodies are produced by B-Lymphocytes (B-Cells).
- Antibodies causes one of several actions to neutralize, eliminate or destroy that antigen.
What is the Function of a B-Cell?
The main purpose of the B-cells are to become sensitized to a specific foreign protein (antigen) and to produce antibodies directed specifically against that protein.
What is the B-Cells lymphocyte pathway?
- Starts out in the bone marrow as stem cells.
- Released into the blood and travel to secondary lymphoid tissues such as spleen, parts of lymph nodes, tonsils and mucosa of the intestinal tract.
Describe the Antigen Recognition stage of the Antibody Mediated Immunity:
- Macrophage recognizes the invader and attaches itself to the antigen.
- Macrophage does not attack but presents the antigen to the helper T-Cell.
- Both will process the antigen to expose the antigen's recognition sites.
After Antigen Recognition, Lymphocyte sensitization occurs. Describes what happens then:
- B- cell recognizes the antigen as a non self and is not sensitized to the antigen.
- B- cells can only be sensitized to one type of antigen.
Whenever some substance with the same antigen as the B-cell enters the body and recognized. the B-cell gets activated.
B-cells starts to divide and form Plasma cell
and Memory Cell
What is the function of Plasma Cell?
- comes from sensitized B-cell.
- produces antibodies against the sensitizing antigen.
What is the function of Memory Cell?
is a sensitized B-cell but does not start to function until the next exposure to the same antigen.
After Lymphocyte Sensitization, Antibody Production and Release is next. Describe the processes:
Plasma Cells produce antibodies which then gets released into the blood and other body fluids as free antibody (Humoral Immunity).
Circulating antibodies can be transferred from one person to another to provide the receiving person with immediate immunity of short duration (3-30 days)
Antibody antigen binding:
antibodies are Y shaped molecules and the tips recognize specific antigen and binds to it. The step or Fc Fragment can bind to WBC's receptor sites which then will have surface antigens that can stick to antigens and attack the antigens.
Antibody-binding actions are triggered by binding of antibody to antigen. What happens then?
The antibody will be neutralized, eliminated or destroyed.
- these actions include:
- agglutination, lysis, complement fixation, precipitation and inactivation or neutralization.
what is agglutination? and what is the purpose?
- antibody clumps together the antigen forming immune complexes.
- it slows the movement of the antigen through body fluids
- the irregular shape increases the change of the complex being attacked by other WBC's
What is lysis?
cell membrane destruction.
- the binding of antibodies creates holes in the membrane.
- It requires a complement be activated and fixed to the immune complexes. Bacteria and viruses are most affected by this.
complement activation and fixation
are actions triggered by some classes of antibodies that can remove or destroy antigen. IgM and IgG are the classes of antigen that can do so.
When these antigen binds, they present binding sites for the first component of complement. A cascade of other protein complements will start to activate as well.
similar to agglutination but antibody molecules bind so much antigen that large, insoluble, antigen-antibody complexes are formed. They cannot stay in suspension in blood and instead be acted on and removed by neutrophils and macrophages.
makes antigen harmless without destroying it.
Sustained immunity (memory)
memory B-cells remain sensitized to the specific antigen to which they were originally exposed. on re-exposure, the memory cells rapidly respond.
First, they divide and form new sensitized blast cells and new sensitized plasma cells.
blast cells continue to divide producing many more sensitized plasma cells. and then it can rapidly make large amounts of antibody specific for the sensitizing antigen.
Because pf memory cells, we do not worry even upon multiple re-exposure because the anamnestic (immune) response tp the antigen.
Two types of immunity:
- Innate- native immunity (natural)
- Adaptive immunity
Innate- native immunity aka natural immunity
- The inborn ability of the body to protect oneself from invasions
- Cannot be transferred from one person to another
- not an adaptive response to exposure or invasion by foreign protein
skin, mucosa, antimicrobial chemicals on the skin, complement and natural killer cells.
Immunity that the body learns to make or receives as an adaptive response to invasion by organisms or foreign proteins.
The difference between Natural and Artificial:
- Occurs when antigens enter the body and the body responds by making specific antibodies against the antigen.
- The body is actively working to protect oneself.
- Natural Active immunity: exposure to antigen, body synthesizes, long term protection
- Artificial: contact with (attenuated) vaccine, takes weeks to develop, lasts years (boosters)
Diff bet. Natural and Artificial:
- occurs when antigen enters the body without the assistance and the body responds by actively making antibodies against that antigen.
- Natural: Ready-made mother to fetus via placenta, mother to infant via colostrum. long lasting.
- Artificial: antibodies given (IM), immediate, temporary
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