Question

Draw a representation of what occurs in "The Antibody Reaction" step in cells where a reaction occurred. Label all parts appropriately. Describe what occurs in those cells in which there is a reaction. Why is there no reaction in the other cells?

Answer 1

Antigen B cell maturation Antibody secretion APC r,イ Complement fixation Antigen re-presentation! (1) Opsonization (2) Membrane FcYR attack complex (3) Release C3a, C5a for chemotaxis Release of . inflammatory mediators e.g. TNF-α, interleukins, etc. Phagocytosis ADCC Target cell lysis Inflammation

Antibody reaction is a chemical interaction of antibodies secreted from B-cells and antigens during an immune response. Various types of antigens and antibodies are produced but each antibody only binds to its specific antigen.

Humoral immunity or antibody-mediated immunity reaction involves the following steps:

• When a B- cell encounters an antigen it gets activated.
• By endocytosis, a B-cell engulf and digests the antigen
• Antigen fragments bound to their unique MHC (membrane histocompatibility molecules) are displayed here.
• This combination of antigen and MHC attracts the mature compatible T- cells
• Activated T-cells secretes cytokines, help the B-cells to multiply and mature into plasma cells secreting antibodies.
• These antibodies are then released into the blood. These antigens bid with their specific antigens forming antigen-antibody complexes, which are cleared by complement cascade or in spleen and liver.

Binding of antibodies to antigens inactivates antigens by Neutralization coating of bacteria and blocking of viral binding sites Precipitation of dissolved antigens Microbial agglutination Complement system activation Complement molecule Bacteria Virus Antigen malecules Bacterlum Foreign cell Hole Enhances Leads to Phagocvtosis Cell lysis Macrophage

The cells undergoing antibody reaction cause agglutination (in case of red blood cells) also called as clumping the antibody reaction may lead to phagocytosis or cell lysis. whereas the cells in which antibody reaction has not occurred doesn't show agglutination. As a result, the cell will not lyse or phagocytose.