ch 15
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The two branches of acquired and specific immunity? Which one is involvement in humoral immunity and which in cell mediated immunity?
B cell- Humoral T cell- cell mediated
Receptor MHC I Tissue distribution? Type of antigen presented? Type of T cell and T cell marker interacted with?
Tissue distribution: on all nucleated cells Type of antigen presented: intracellular antigens Interacts with: T cells and CD8
Receptor MHC II Tissue distribution? Type of antigen presented? Type of T cell and T cell marker interacted with?
Tissues distribution: on lymphocytes Type of antigens presented: foreign antigens Interacts with: T cell and CD4
to summarize MHC I receptor
• Most important for killing of virus-infected cells and tumor cells • widely distributed in our body, reason for organ rejection • Involves Cytotoxic T Lymphocytes (CTL) (CD8+)
B cell receptors and antibodies: structural features of an immunoglobulin molecule
Y-shaped 4 polypeptide chains: 2 heavy + 2 light Variable (V) regions: bind antigen Constant (C) regions: define class; bind immune cells Fab region: antigen-binding “arms” Fc region: constant stem; binds Fc receptors on immune cells & complement
antigen independent stage
Occurs in embryo/infant DNA recombination (gene shuffling) creates millions of unique BCR & TCR clones No antigen needed yet
maturation
immature T and B cells differentiate into receptor bearing cells in thymus or bone marrow, but still exist in the resting state B cell mature in bone marrow T cell mature in thymus
do human B cells mature in the bursa of Fabricius
Human B cells do NOT mature in the bursa of Fabricius (that is in birds).
antigen dependent stage
Antigen exposure → activation Clonal expansion → plasma cells + memory cells
antigen
substance that provokes an immune response in lymphocytes
What features constitute a “good” antigen (in terms of immunogenicity)?
foreign, large and complex
what are haptens?
foreign molecules less than 1,000 dalton -not antigenic unless attached to a larger carrier
what is a superantigen?
Cause massive, nonspecific T-cell activation → cytokine storm examples: toxic shock syndrome and some autoimmune diseases
what is an allergen?
antigen that provokes allergy example: pollen and peanuts
the two types of cells generated when a resting naïve B cell is activated
Plasma cells Memory B cells
What is the function of plasma cells?
secrete and produce antibodies
Why are B memory cells important in the adaptive immune response?
they remember the germ to protect you next time
Fab
antigen binding fragment -variable regions of the heavy and light chains
Fc
crystallizable fragment -anchors Ig to B cells -can also bind to other white blood cells -more constant in sequence -responsible for Ig class identification
Monomer antibody structure (Fab & Fc) and connection to C/V regions
Antibodies are Y-shaped immunoglobulins made of 4 polypeptide chains. -They have 2 functional areas: Fab and Fc. -Fab corresponds to the Variable (V) regions of heavy + light chains. -Fc corresponds to the Constant (C) regions of the heavy chains.
What is the function of Fab? How many Ag-binding sites can be found on each Ig monomer molecule?
Fab is the antigen-binding fragment (Variable regions). Each monomer has 2 Fab arms, so: ➡️ Each Ig monomer has 2 antigen-binding sites.
What is the function of Fc? (What does Fc interact with or bind to?
binds immune cells AND complement AND determines class. -anchors Ig to B cells -can bind to other white blood cells -identifies the Ig class
what are the relationships between Fab/Fc regions & V/C regions?
Fab = Variable (V) regions (antigen-binding) Fc = Constant (C) region (class identity, binds cells/complement) ➡️ Fab ↔ V region ➡️ Fc ↔ C region
Which class(es) of antibodies can fix complement (the classical complement pathway)?
lgG: “can fix complement” lgM: “Associated with complement fixation”