Introduction to the Immune System Flashcards
Define immunity
Ability to respond to foreign substances regardless of the physiologic or pathologic consequence of such a reaction
Define adaptive immunity
Response of antigen-specific lymphocytes to antigen includes memory
Define innate immunity
Protection against antigens that relies on mechanisms that exist before exposure
What is a cluster of differentiation (CD)?
Cell surface molecule expressed on various cell types designated by a CD number. It is used to define cell type, receptors, etc. Recognized by monoclonal antibodies (mAbs)
Define cytokines. Give types of cytokines.
Bioactive protein molecules that mediate immune responses.
Interleukins (IL), tumor necrosis factor (TNF), interferon (IFN)-α, β, and γ, transforming growth factor (TGF)- β, and CSF
What are chemokines?
Chemotactic cytokines. They say “come here.”
Define antigen (Ag)
Define immunogen
Define tolerogen
Not all […] are […]
Ag: A molecule or part of a molecule that is recognized by the immune system.
Immunogen: An Ag that evokes a specific immune response.
Tolerogen: An Ag that induces immunologic tolerance.
Not all Ags are immunogens!!
endogenous Ag vs. Exogenous Ag
Compare autoAgs to alloAgs
Endogenous Ag is the body’s own cellular components or intracellular pathogens (e.g., viruses, intracellular bacteria and parasites). They can further be classified into:
AutoAgs: self-Ag
or
AlloAgs: Tissue specific Ag which is present in one individual of a species, but not in others (e.g., ABO blood groups)
Exogenous Ag enters the body or system and freely circulates in the body fluids until trapped by APCs
List the two branches of the adaptive immune system and examples of artificial and natural immunity from each of those branches
Two branches are passive and active.
Passive artificial: an intravenous injection of Abs
Passive natural: Mom passes Abs to baby through breast milk or through placenta
Active artificial: A vaccine
Active natural: Infection or exposure to pathogen
What are some characteristics of the innate immune system?
Responds rapidly
It is not Ag specific
No immunologic memory
Stimulates the adaptive immune system
What are the 3 different types of phagocytes in the innate immune system?
Neutrophils
Monocytes/macrophages
Dendritic cells
What are the 2 major functions of macrophages?
M1 classical macrophages are induced by innate immunity and play a role in inflammation
M2 alternative macrophages are induced by IL-4 and IL-13 and play a role in tissue repair and control of inflammation
What are the 2 major functions of dendritic cells?
Initiate inflammatory response
Initiate adaptive immune response
What is neutrophil leukocytosis?
Its when neutrophils are released from the bone marrow in greater numbers in response to an infection. Also called a left shift
What type of WBC is first to arrive at the site of an infection?
Neutrophil
What cell type is pus largely composed of, and what CD’s are characteristic of that same cell?
Neutrophils are what pus is largely composed of
CD15+ and CD16b+
List 3 functions of monocytes/macrophages
Garbage collectors when at rest
APCs when activated
Vicious killers when hyper-activated
What cell-surface marker is characteristic of monocytes/macrophages?
What does it bind?
CD14 (TLR4), which recognizes and binds to LPS
What cytokine causes differentiation into eosinophils?
IL-5
Name 2 characteristics of eosinophils
Responsible for combating multi-cellular parasites
Like the mast cells, they play a major role in atopic diseases (allergies)
What are the two types of mast cells?
Tissue and mucosal, depending on the tissue they are residing
What are some ways mast cells can be stimulated to degranulate
Direct injury, chemicals, alcohol, certain antibiotics, cross-linking of IgE receptors, or activated complement (C’) proteins
What are the professional antigen-presenting cells (APCs)
Dendritic cells
Dendritic cells constitutively express high levels of what?
MHC class II and B7
What acts as the bridge between the innate and adaptive immune system?
APCs
What cytokine converts HSCs → CLPs which give rise to all lymphocytes
IL-7
Where do B and T cells mature
Bone marrow and thymus, respectively.
Distinguish between a mature naive lymphocyte, an effector lymphocyte, and a memory lymphocyte
mature naive: lymphocyte which has not been activated by Ag
Effector: Lymphocytes which have been activated by Ag and can now perform their function
Memory: “immunity”
Distinguish between humoral and cell-mediated immunity
Humoral: Abs neutralize and eradicate exogenous Ags
Cell-mediated: eradication of endogenous Ags which is done by T-cells and macrophages
Broadly, what do B-cells do?
Neutralization of microbe, phagocytosis, complement activation
Broadly, what do helper (CD4+) T cells do?
Activation of macrophages, inflammation, activation of T and B cells
Broadly, what do cytotoxic (CD8+) T cells do?
Kill infected cells
Broadly, what do Treg cells do?
Suppress the immune response
What CD markers are present on B cells?
CD19+, CD20+
What CD markers are present on all T cells?
CD3+
What CD markers are present on all T helper (CD4+) cells
CD3+, CD4+
What is the cytokine secretion profile of Th1?
IL-2, IFN-γ
What is the cytokine secretion profile of Th2?
IL-4, IL-5, IL-13
What is the cytokine secretion profile of Th17?
IL-17, IL-22
What CD markers are present on Treg cells?
What is their cytokine secretion profile?
CD3+, CD4+, CD25+
IL-10, TGF-β
What CD markers are present on cytotoxic (CD8+) T cells?
CD3+, CD8+
What is the purpose of the lymphatic system?
Drain all tissues and transport lymphocytes and Ags to secondary lymphoid tissue where lymphocytes can interact with Ag
What is the role of natural killer (NK) cells in the innate immune system?
What activates NK cells and what do activated NK cells secrete in return?
The role is to recognize infected, stressed, or malignant cells and kill them. It does this via the release of granzymes and perforins that lead to apoptosis of target cell
NK cells are activated by IL-12 (from macrophages), IL-15, IL-18 and type I IFNs
Activated NK cells secrete IFN-γ which activates macrophages
What is the role of NK cells in adaptive immunity
They are the principle mediator of ADCC: activating receptor of IgGFc
What are the CD markers found on the surface of NK cells
CD16+, CD56+
Differentiate between primary and secondary immune responses
Primary immune response: first time an Ag is encountered. Causes activation of naive cells to perform their effector function. Also generates memory cells. Takes about 2 weeks
Secondary immune response: Second time Ag is encountered. Activates the memory cells and causes a stronger, faster effector response. We see a robust response in about a week.
What type of immunity does not result in memory cells being produced for subsequent exposures?
Passive immunity
