Cell Signaling & Receptors
What is the term for any event that instructs a cell to change its metabolic or proliferative state?
Cellular Signal
What two signals are required for naïve T cell activation?
Antigen recognition via TCR and co-stimulation via CD28
What cytokine is primarily responsible for macrophage activation?
IFN-gamma
What are the three pathways that activate complement?
Classical, Alternative, Lectin
What are the five major antibody isotypes?
IgG, IgA, IgM, IgE, IgD
What are the three major types of receptor changes induced by ligand binding?
Conformational change, dimerization/clustering, translocation in membrane
Which molecules are essential for TCR signal transduction?
CD3 and CD28
What are the three major pathways regulated by the Jak-STAT system?
MAP kinase, Jak-STAT, PI3K
What is the role of C3 convertase in the complement system?
Cleaves C3 into C3a and C3b, amplifying the response
Which antibody isotype is most abundant in serum?
IgG
What is the effect of lower Kd on receptor-ligand binding?
Lower Kd means stronger
What is the function of CD28 in T cell activation?
Provides co-stimulation by binding B7 molecules on APCs
What is the function of SOCS proteins in cytokine signaling?
They suppress cytokine signaling
Which complement component forms the Membrane Attack Complex?
C9
What is the primary function of IgA?
Provides mucosal immunity and is found in secretions
What role do ITAMs play in receptor signaling?
They act as docking sites for kinases in immune signaling
What kinase is specific to B cell activation?
Syk (Spleen Tyrosine Kinase)
Which cytokines are involved in the acute phase response?
IL-1, IL-6, TNF-alpha
Which complement fragment acts as an anaphylatoxin?
C3a and C5a
Which antibody mediates allergic responses?
IgE
What is an example of a cytokine that upregulates receptor expression in immune responses?
IL-2
What are the two primary types of B cell activation?
T-dependent and T-independent activation
What is the function of C-reactive protein in innate immunity?
Binds to phosphocholines and promotes phagocytosis
What type of pathogens are most susceptible to complement-mediated lysis?
Gram-negative bacteria
What is the term for regions on an immunogen recognized by lymphocytes?
Epitopes
A researcher is studying a novel ligand-receptor interaction in immune cells. She finds that after ligand binding, the receptor undergoes a conformational change, leading to the recruitment of intracellular signaling proteins. Which of the following best describes the immediate consequence of this interaction?
A) Activation of mitogen-activated protein kinases (MAPK)
B) Increased expression of cytokine receptors
C) Direct activation of the complement cascade
D) Secretion of antibodies by plasma cells
A) Activation of mitogen-activated protein kinases (MAPK)
A patient with a genetic mutation affecting CD28 expression on T cells is found to have recurrent viral infections. Which of the following best explains why the lack of CD28 contributes to increased susceptibility to infections?
A) CD28 is required for antigen processing and presentation by antigen-presenting cells.
B) CD28 is necessary for the co-stimulation required to activate naïve T cells.
C) CD28 enhances B cell receptor signaling, promoting antibody production.
D) CD28 inhibits T cell proliferation, preventing excessive immune responses.
B) CD28 is necessary for the co-stimulation required to activate naïve T cells.
A scientist is developing a drug that blocks the Jak-STAT pathway in immune cells. Which of the following effects would most likely be observed in a patient receiving this drug?
A) Enhanced T cell proliferation and differentiation
B) Decreased cytokine-mediated immune signaling
C) Increased activation of macrophages and neutrophils
D) Overproduction of interferons leading to chronic inflammation
B) Decreased cytokine-mediated immune signaling
A patient with recurrent bacterial infections is found to have a deficiency in C3, a central component of the complement system. Which of the following consequences is most likely associated with this deficiency?
A) Impaired ability to form the membrane attack complex (MAC)
B) Increased susceptibility to viral infections due to reduced interferon signaling
C) Reduced inflammation due to lack of cytokine production
D) Failure of B cells to recognize antigens
A) Impaired ability to form the membrane attack complex (MAC)
A researcher isolates a monoclonal antibody from a patient and finds that it lacks a functional Fc region. Which of the following functions will most likely be impaired as a result?
A) The antibody’s ability to recognize and bind its specific antigen
B) The antibody’s ability to activate the complement system
C) The antibody’s ability to undergo somatic hypermutation
D) The antibody’s ability to enter the bloodstream
B) The antibody’s ability to activate the complement system