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Humoral Immune Response

Humoral Immune Response . Terry Kotrla, MS, MT(ASCP)BB Fall 2006. Humoral Immunity . 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.

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Humoral Immune Response

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  1. Humoral Immune Response Terry Kotrla, MS, MT(ASCP)BB Fall 2006

  2. Humoral Immunity • 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.

  3. Dynamics of Antibody Production • Primary immune response • Latent period • Gradual rise in antibody production taking days to weeks • Plateau reached • Antibody level declines

  4. Dynamics of Antibody Production • 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.

  5. Secondary Response • 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

  6. Humoral Immune Response

  7. Dynamics of Antibody Production

  8. Cellular Events • Antigen is “processed” by T lymphocytes and macrophages. • Possess special receptors on surface. • Termed “antigen presenter cell” APC. • Antigen presented to B cell

  9. Basic Antibody Structure • Two identical heavy chains • Gamma • Delta • Alpha • Mu • Epsilon

  10. Basic Antibody Structure • Two identical light chains • Kappa OR • Lambda

  11. Basic Antibody Structure

  12. Basic Structure of Immunoglobulins

  13. Papain Cleavage • Breaks disulfide bonds at hinge region • Results in 2 “fragment antigen binding” (Fab) fragments. • Contains variable region of antibody molecule • Variable region is part of antibody molecule which binds to antigen.

  14. Papain Cleavage

  15. Pepsin • Breaks antibody above disulfide bond. • Two F(ab’)2 molecules • The rest fragments • Has the ability to bind with antigen and cause agglutination or precipitation

  16. Papain and Pepsin Cleavage

  17. IgG • Most abundant • Single structural unit • Gamma heavy chains • Found intravascularly AND extravascularly • Coats organisms to enhance phagocytosis (opsonization)

  18. IgG • Crosses placenta – provides baby with immunity for first few weeks of infant’s life. • Capable of binding complement which will result in cell lysis • FOUR subclasses – IgG1, IgG2, IgG3 and IgG4

  19. IgG

  20. IgA • Alpha heavy chains • Found in secretions • Produced by lymphoid tissue • Important role in respiratory, urinary and bowel infections. • 15-10% of Ig pool

  21. Secretory IgA • Exists as TWO basic structural units, a DIMER • Produced by cells lining the mucous membranes.

  22. Secretory IgA

  23. IgA • Does NOT cross the placenta. • Does NOT bind complement. • Present in LARGE quantities in breast milk which transfers across gut of infant.

  24. IgM • Mu heavy chains • Largest of all Ig – PENTAMER • 10% of Ig pool • Due to large size restricted to intravascular space. • FIXES COMPLEMENT. • Does NOT cross placenta. • Of greatest importance in primary immune response.

  25. IgM

  26. IgE • Epsilon heavy chains • Trace plasma protein • Single structural unit • Fc region binds strongly to mast cells. • Mediates release of histamines and heparin>allergic reactions • Increased in allergies and parasitic infections. • Does NOT fix complement • Does NOT cross the placenta

  27. IgE

  28. IgD • Delta heavy chains. • Single structural unit. • Accounts for less than 1% of Ig pool. • Primarily a cell bound Ig found on the surface of B lymphocytes. • Despite studies extending for more than 4 decades, a specific role for serum IgD has not been defined while for IgD bound to the membrane of many B lymphocytes, several functions have been proposed. • Does NOT cross the placenta. • Does NOT fix complement.

  29. Cellular Immune Response • Important in defending against: fungi, parasites, bacteria. • Responsible for hypersensitivity, transplant rejection, tumor surveillance. • Thymus derived (T) lymphocytes

  30. Cell Mediated Reaction • Helper T cells – turn on immune response • Suppressor T cells – turn off immune response • Cytotoxic T cells directly attack antigen

  31. Cell Mediated Immunity

  32. Lymphokines

  33. Summary • http://www.biology.arizona.edu/immunology/tutorials/immunology/page2.html

  34. http://www.jdaross.cwc.net/humoral_immunity.htm • http://academic.brooklyn.cuny.edu/biology/bio4fv/page/aviruses/cellular-immune.html • http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect23.htm

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