Lymphatic system part 4

a special class of cells that process and present exogenous antigens.  they include dendrites macrophages and B cells.  They are strategically located in places where antigens are likely to penetrate the innate defences and enter the body.

are small protein hormones that stimulate or inhibit many normal cell functions, such as cell growth and differentiation

is the process by which a lymphocyte proliferates and differentiates in response to a specific antigen.  The result is the formation of a clone of cells that can recognize the same antigen as the original lymphocyte

antigen receptors on the surface of T-cells recognize and bind to specific foreign antigen fragments that are presented in MHC complexes.  Each T-cell has its own unique TCR that can recognize and bind to the antigen

a T-cell becomes activated only if it binds to the foreign antigen and at the same time receives a second signal, a process known as this.

a costimulator of cytokines

is a type of protein present on helper T-cells. Most T-cells that display this develop into helper T-cells once stimulated

secrete a variety of cytokines.  One important cytokine produced is interleuken-2

are not active t-cells.  However, if the same antigen enters the body again in the future, these cells can quickly proliferate and differentiate into more active helper T cells and more of these cells.

a toxic molecule released by cytotoxic t-cells which activates enzymes in the target cell that cause the target cell's DNA to fragment and the cell dies

T-cells that display CD8 develop into these

Involves B-cells in the presence of a foreign antigen, a specific B-cell in certain tissues becomes activated.  Then it undergoes clonal selection, forming a clone of plasma cells and memory cells.  Plasma cells are the effector of a B-cell, they secrete specific antibodies which in turn circulate in the lymph and blood to reach the site of invasion

during activation of a B-cell, antigens bind to these. Then it is taken into the cell broken down into peptides and combined with MHC-2 self antigens and moved to the B-cell membrane. Helper T-cells recognize the MHC 2 complex and deliver the costimulation needed for B-cell proliferation and differentiation

when a normal cell transforms into a cancerous cell, it often displays, novel cell surface components called these.  These molecules are rarely if ever displayed on the surface of normal cells

can combine specifically with the epitope on the antigen that triggered its production

the reaction of antibody with antigen blocks or neutralizes some bacterial toxins and prevents attachment of some viruses to body cell

if antibodies form against the antigens on the cilia or flagella of motile bacteria, the antigen-antibody reaction may cause the bacteria to lose their motility which limits their spread to nearby tissue

because antibodies have two or more sites for binding to antigen, the antigen-antibody reaction may cross link pathogens to one another causing this.  Phagocyte cells ingest these microbes more readily

antigen-antibody complexes initiate the classical pathway of the complement system

the stem region of an antibody acts as a flag that attracts phagocytes once antigens have bound to the antibodies variable region. Antibodies enhance this by agglutination and precipitation  by activating complement and by coating microbes so that they are more susceptible.

is a defence system made up of over 30 proteins produced by the liver and found circulating in blood plasma and within tissues throughout the body.  Collectively these proteins cause phagocytosis, cytolysis and inflammation

a hallmark of the immune respons is memory for specific antigens the have triggered immune responses in the past.  it is due to long lasting antibodies and very long lived lymphocytes that arise during clonal selection of antigen-stimulated B-cells and T-cells

after an initial contact with an antigen no antibodies are present for a period of several days.  Then slow rise in the antibody titers occurs followed by a gradual decline in antibody titer

the amount of antibodies in serum

after subsequent encounters, the antibody titer is far greater than during a primary response and consists mainly of IgG antibodies.  This is an accelerated more intense response.