Microbiology Chapter 21.txt

Antigens are microbes or microbe parts that provoke an immune response

Proteins made against antigens

• Protein
• Carbs provoke a little response and lipids a very poor response

• Less than 10000 molecular weight, so no immune response
• We don't build antibodies to haptens
• Can attach to something else to provoke an immune response

• Epitopes
• Protein receptors on B and T cells recognize discrete regions of the antigen called epitopes

• Non immunogenic molecules that don't stimulate the immune system by themselves, but when they are linked to proteins in the body, the larger combination may be recognized as nonself.
• Specific immunologic tolerance
• An example is penicillin

The ability to remember past pathogen exposures

• Refers to lymphocytes capable of reacting with a specific epitope
• B and T cells are waiting in the wings to respond to an antigen

Exposure to an antigen only activates those naive B and T cells with receptors recognizing specific epitopes on the antigen.

Body attacks self

The loss of the body's ability to respond to antigens and epitopes

Other T cells from attacking "self" cells

Self-tolerance breaks down

• They may not be recognized as "self"
• Thus they might provoke an immune response (allergies)

• The ability to "remember" past pathogen exposures
• The body fights off any subsequent infections

• Activation of B cells
• Production of antibodies against the identified antigen

Lysis of infected or abnormal cells

Antibodies are useless

Eliminate "nonself" cells

• Involved in producing antibodies against epitopes
• Humoral immunity

Cell mediated immunity

In the lymph nodes and spleen

When an antigen is detected

• React quickly when activated
• Memory cells
• Plasma cells
• Each B cell can produce only one type of antibody

• Produced from B cell clones
• Synthesize and secrete antibodies against the invading pathogen
• B cells that make antibodies
• Makes about 2000/second
• Live about 4 days

• Are long lived B and T cells capable of dividing on short notice to produce more effctor cells and additional memory cells in an immune response
• Can live for decades

• Target the pathogen
• B and T cells contain activated lymphocytes that will develop into effector cells and memory cells.

• Lymphocytes originate from these cells in the yolk sac, but end up in the bone marrow
• Develop into myeloid and lymphoid progenitors

• Developed from Hematopoietic stem cells
• Become red blood cells and most of the white blood cells

Become lymphocytes of the immune system

• The variable domains in a light and heavy chain forma highly specific, three-dimensional structure
• It is this region on the antibody that binds to the antigen with epitopes

Only T and B cells with receptors that recognize specific epitopes on that antigen

• Effector cells that which target pathogens
• Memory cells are long-lived B and T cells
• They are capable of division on short notice

• Groups of stem cells
• Hematopoietic stem cells

Hematopoietic stem cells in the yolk sac and bone marrow

The thymus

The bone marrow

• Immunoglobulins, (Ig)
• Hooked together with a disulfide bond

17 % of protein in serum

• 2 identical heavy (H) chains
• 2 identical light (L) chains

• Immunoglobulins
• Results in the activation of B cells and the production of antibodies that recognize epitopes on the identified antigen in the blood or lymphatic fluids
• The response is so specific that the body can generate antibodies to just about any antigen or epitope it encounters.

Determines the destination (body location) and functional class of the antibody

• Contains different amino acids for the many antibodies produced
• Binds to antigen
• Each variable region can bind to two antibodies

• A constant region, which determines the location and functional class of the antibody
• A variable region, which contains different amino acids for the many antibodies produced

Formation of the specific antigen binding site

The Epitope

Opsonization

• Able to be crystalized
• It can combine with phagocytes, activate the complement system or attach to certain cells in allergic reactions

There are five immunoglobulin classes

• Is the first (but short-lived) Ig to appear in circulation after B cell stimulation
• Primary antibody response
• Largest Ab in circulation
• Doesn't cross the placenta
• 5 chains

• Is the major circulating antibody
• It provides immunity to the fetus and newborn. Crosses the placenta
• 1st discovered. Classical
• 80% of all Ig's in the blood
• A little slow, takes 24-48 hours
• Secondary Ab response

IgG memory cells provide long term resistance

• Provides resistance in the respiratory and gastrointestinal tracts
• It is found in colostrum & tears
• 2 chains hooked together J chain

Plays a role in allergic reactions

Don't know

• The first time the body encounters a pathogen
• B cells are activated and effector cells, the plasma cells, start producing and secreting antibody

• More powerful and longer lasting
• It occurs with a subsequent infection by the same pathogen
• Due to the presence of memory cells, a rapid response to antigen leads to the production of IgG principle antibody.

Gene arrangements

• A random mix and match of gene segments to form unique antibody genes
• This accounts for the large number of unique antibodies encoded by immune system genes
• The information encoded by these genes is expressed in the surface receptor proteins of B cells and in the antibodies later expressed by the stimulated clone of plasma cells.

• 300 Variable
• 50 diversity
• 4 joiner
• 8 constant regions

Antibodies react with molecules at the viral surface and prevent the viral attachment to cells

Forms pores in the bacterial cell membrane increasing cell membrane permeability and inducing the cell to undergo lysis through the unregulated flow of salts and water

Proteins that define the uniqueness of the individual and play a role in the immune response

• MHC-II molecules fold to form a pocket in which small antigen (peptide fragments can bind)
• APCs present antigen fragments to CD4 T cells which will bind them with their TCR/CD4 receptor complex

• Molecules that are found on all nucleated cells of the body
• Fold so that they can bind a small antigen fragment from an infecting virus

A cytokine which binds with naive T cells and stimulates T-cell activation

• T2: Help in the activation of humoral immunity
• T1: Recognize and bind to infected APC displaying the appropriate MCH-1 peptide

• Toxic proteins that insert into the membrane of the infected cell forming cylindrical pores in the membrane
• This releases ions, fluids, and cell structures

Cytotoxic cells release granzymes that enter the target cell and trigger apoptosis.

Antibodies called antitoxins combine with toxins and neutralize them and prevent toxin attachment to cells

Antibodies coat bacterial cells and prevent bacterial attachment to cells

Antibodies combine with antigens on the cell surface and bind the cells together or restrict movement.

• Antibodies combine with dissolved antigens to form lattice like arrangement that precipitate out of solution.
• Each Antibody attaches to two antigens.
• Deals with something smaller than a cell

The Fc portion on antibodies encourages phagocytosis by forming a bridge between antigen and receptor sites on the phagocyte.

• Antitoxins
• Agglutination
• Precipitation
• Opsonization
• The complement system

• Death
• Inactivation
• Increased susceptibility

• Cytotoxic T cells
• Delayed hypersensitivity T cells
• Naive cells, (Helper T cells)
• Suppressor T cells

• Killer T cells
• The marines
• Cytotoxic T cells have T-cell receptors (TCRs) and CD8 coreceptor proteins

• Stimulates B cells and cytotoxin cells
• Makes other cells not lazy
• Have TCRs and CD4 coreceptor proteins
• Formerly known as helper T cells can help with both humoral and cell mediated immunity
• HIV attaches to the CD4 receptor and infects the cell

Keeps other T cells from getting too active so they don't attack self

• Cytotoxic T cells
• Naive T cells

Effector T Cells