16.12 Immune system Flashcards
innate immunity
Lysozymes (saliva, blood, tears) Skin Acidity of stomach Macrophage/neutrophils Complement system (20 blood proteins)
Humoral (ANTIBODIES)
Ab, Ig
antibodies detect protein sequence AND folding
Binding of antigen causes:
- inactivation of antigen (viral coat)
- induce phago by macrophage or neutrophil
- activate complement system, which punctures the antigen’s cell membrane
B cell development
derived from stem cells in bone marrow
recombination of many small segments; many clones with DIFFERENT variable regions
B and T cells do NOT possess the same copy of the genome!
Clonal selection (antigen binds to antibody…)
that cell proliferates, differentiating into PLASMA cells and MEMORY cells
plasma cells produce and secrete antibody protein into the plasma; memory cells have same variable region, but do NOT secrete antibody – they remain dormant, but will produce antibody quickly when detecting the antigen
Clones have different recognition sequences
antibody structure
Light chain bound to heavy chain by DISULFIDE linkages
T cell
CELL-MEDIATED IMMUNITY
T HELPERS (CD4)
T KILLERS (CD8, cytotoxic)
T helper
activates B cells, T killer cells, and other cells of the immune system - CENTRAL TO WHOLE IMMUNE RESPONSE
releases special hormones called LYMPHOKINES and INTERLEUKINS
a target of HIV
T killer
DESTROYS abnormal HOST cells Attacks: - Virus-infected host cells - Cancer cells - Foreign cells such as grafts
MHC I and II
MHC I - proteins of MHC I are found on the SURFACES of all nucleated cells in the body, which pick up random peptides from inside the cell and displays them on surface, allowing T cell to monitor cellular contents. T killer cell can detect the viral proteins and activate/proliferate.
Cytotoxic T cell MONITORS CELLULAR CONTENTS
MHC II is more complex. APCs have MHC II. APCs include macrophages and B cells, who p-tize cells, chop them up, and display fragments using MHC II display system, which T helpers recognize and bind to. The T helper is activated by antigen displayed in MHC II and activates B cells (which stimulate proliferation of T killer cells) specific for that antigen.
T helpers are ONLY ACTIVATED BY ANTIGEN PRESENTED BY MHC II (!)
Activated B cells mature into plasma cells and secrete antibodies specific for the antigen.
MHC I and II
MHC I - proteins of MHC I are found on the SURFACES of all nucleated cells in the body, which pick up random peptides from inside the cell and displays them on surface, allowing T cell to monitor cellular contents. T killer cell can detect the viral proteins and activate/proliferate.
Cytotoxic T cell MONITORS CELLULAR CONTENTS
APCs have MHC II. APCs include macrophages and B cells, who p-tize cells, chop them up, and display fragments using MHC II display system, which T helpers recognize and bind to. The T helper is activated by antigen displayed in MHC II and activates B cells (which stimulate proliferation of T killer cells) specific for that antigen.
T helpers are ONLY ACTIVATED BY ANTIGEN PRESENTED BY MHC II (!)
Activated B cells mature into plasma cells and secrete antibodies specific for the antigen.
Primary versus secondary immune response
Primary is too slow to prevent symptoms. Takes 2 weeks, leads to generation of memory cells.
Secondary = “Immune”, given presence of memory cells
Spleen
FILTERS BLOOD, site of immune cell interactions, which is like a lymph node
DESTROYS aged RBCs
Thymus
T cell maturation (most active in children)
Tonsils
“catch” pathogens from respiration and ingestion
