Microbiology Final- Chapter 15

Antigen Presenting Cell

Cells that can endocytose or phagocytose an antigen to T cells, and activate T Cells. (Macrophages, Dendritic cells, B cells)

Agglutination

Clumping together of RBD, or bacteria, usually in response to a particular antibody.

Class 2 MHC

Found on antigen presenting cells (B cells, dendritic cells, macrophages)

Describe the secondary immune response

secondary response - second time the antigen is encountered (1) no lag period (2) IgM is produced by newly activated B cells; IgG by memory cells (3) more memory cells are formed. (4) antibody produced sooner and in higher amounts; found for longer periods of time in the serum (5) often the person does not realize they have been infected - the immune system clears the infective agent before it can do damage. (6) more memory cells are formed

Opsonization

Immune process where opsonins bind to the surface of the antigen so that the antigen will be readily identified and engulfed by phagocytes for destruction.

B cells

Lymphocytes in mature humans in the the bone marrow, can be antigen presenting cells. Activated by TH cells, mature to antibody producing cells.

T cells

Lymphocytes, differentiate from stem cell in bone marrow. Mature in the thymus, then travel to lymphatic tissues

Plasma cells

Mature antibody producing cells

Antigen

Molecules that invoke an immune response and have multiple epitope sites.

lgG (bacteria and viruses)

Monomer, long-term immunity, memory antibodies

lgA (bacteria and viruses)

Monomer, secretory antibody; on mucous membrane

lgD (parasitic worms)

Monomer- Receptor on B cells

lgE (parasitic worms)

Monomer- antibody of allergy: worm infections

lgM (bacteria and viruses)

Pentamer, produced at 1st response to lgM antigen, can serve as B cell receptor.

Epitope

sites on molecule that are recognized by different antibody molecules.

Precipitation

Precipitan is an antibody that reacts with an antigen to form a precipitate.

Antibody

Proteins synthesized and excreted by B cells, bind to specific antigens

Describe the role of cytotoxic T cells

a. an antigen presenting cell phagocytose and processes an antigen such as a virus, and places peptide of the antigen in an MHC molecule in its membrane b. the APC migrates to the lymph node or other lymphatic tissue and present the antigen in MHC to cytotoxic T-cells c. Cytotoxic T cells in the lymph node express receptors that are specific for a particular antigen d. a cytotoxic T cell that has a receptor that recognized the antigen+ MHC will bind to the dendritic cell. The binding signals plus cytokines signals the cytotoxic T cell to become activated. e. activated cytotoxic T cell clones itself, they leave the lymph node and seek and destroy virally infected or abnormal cells f. recognition of antigen by its receptor signals a cytotoxic T cell to degranulate - secrete perforins and Granzymes that kill the target cell

Explain the functions of antibodies in protective immune reactions

a. antibodies specifically bind to antigen b. antibodies can neutralize - by binding to and blocking attachment sites on a microbe or virus c. antibodies can precipitate of agglutinate antigens, stopping their activity and allowing them to be phagocytosed d. antibodies bind to an opsonize antigens, making it easier for cells to phagocytose them e. antibodies can activate the complement cascade

What are memory cells are and why they are important?

a. memory cells are formed with either T cells or B cells are activated. b. They are important for future exposure to the same antigen because they respond very quickly to the presence of the antigen and the B cells produce protective antibodies

Class 1 MHC

found on all nucleated human cells

MHC (major histocompatibility complex)

glycoproteins found on all cells except RBC. Function as self-makers and to present antigens (peptides) to T cells. 2 Classes

5 classes of antibodies

lgG, lgA, lgM, lgD, lgE

Describe B cell activation

-First phase: a B cell in the lymphatic tissue endocytoses an antigen, processes it, and presents the antigen with MHC in its membrane. -Second phase: the presenting B cell seeks T cells. If an activated T cell can recognize the antigen on the B cell, the T cells secretes cytokine and activates the B cell -The B cell clones itself -some members of the clone differentiate to memory B ells; some to plasma cells that secrete specific antibody.

Describe helper T cell activation

-an antigen presenting cell phagocytose and processes an antigen, and places peptide of the antigen in an MHC molecule in its membrane. -the APC migrates to the lymph node or other lymphatic tissue and present the antigen in MHC to T-cells -T cell in the lymph node express receptors that are specific for a particular antigen -a T cell that has a receptor recognized the antigen + MHC will bind to the dendritic cell. The binding signals plus cytokines signals the T cell to become activated. -The helper T cell (CD4+ T cell), clones itself, and the clone of T cells differentiate to several different subsets of activated T cell, including memory T cells and B cell activating T cells. -Activated T helper cell will find a B cell that is presenting the antigen it recognizes, secretes cytokines, and activates the B cell.

Describe the primary immune response

primary response = first time the antigen is encountered (1) lag period of about 10 -14 days, with no measurable antibody in the serum (2) IgM is produced first, followed by IgG (3) memory B and T cells are formed (4) after several weeks, there is no more measurable antibody in the serum

Lymphocyte

B and T cells