Chapter 43By Ben Karlsberg

Compliment system Consists of roughly 30 proteins in blood

plasma that function together to fight infections

Activated by substances on the surfaces of microbes

Inflammatory response Swelling from a wound Histamine (chemical signal) released from

mast cells (connective tissue cells that store chemicals in granules for secretion)

Capillaries widen and phagocytes are released

Phagocytes engulf bacteria, dead cells, and cellular debris as tissue heals

Natural Killer Cell Kills cells that don’t express class I MHC

protein because infected cells often lose this protein

Lymphocytes T-cells are lymphocytes that migrate from

bone marrow to the thymus to mature B-cells mature in bone marrow Cytokines are released by phagocytic cells

to activate and recruit lymphocytes

Immunoglobulin (antibody) Recognize epitopes (antigenic determinant)

of antigens and bind to them Very specific B-cells recognize epitopes in intact

antigens T-cells recognize epitopes in small antigen

fragments

5 classes of antibodies

Major histocompatibility (MHC) molecules

Class I MHC display peptide antigens to cytotoxic T-cells

Class II MHC display antigens to helper T-cells

Short and long term responses Effector cells- attack antigen instantly –

short living Memory cells- bear receptors specific for an

antigen- long living

Helper T-cells Make CD4 (surface protein that enhances

binding to class II MHC molecules) Activated helper t-cells secrete different

cytokines that stimulate other lymphocytes

Cytotoxic T-cells Make CD8, enhances binding to Class I

MHC Activated- secrete proteins that initiate

destruction of target cells

B-cells Clonal selection of B-cells generates

antibody-secreting plasma cells Binding of antibodies to antigens leads to

elimination by phagocytosis and compliment-mediated lysis

Autoimmune disease HIV- destroys helper t-cells AIDS – Acquired Immunodificiency

syndrome interferes with cell communicated defenses