Cells of the Immune System Flashcards
What do BM stromal cells do?
provide support and growth factors for HSC maintenance and differentiation
What are the fates of the common myeloid progenitor?
Thrombocytes, Erythrocytes, Mast cells, or
Myeloblast, which gives rise to: Basophils, Eosinophils, Neutrophils, Macrophage, Myeloid dendritic cell
What are the fates of the common Lymphoid progenitor?
Lymphoid dendritic cell, NK cell, T cell, B cell –> Plasma cell
What cytokines are required for myeloid differentiation?
IL-3, GM-CSF
What cytokine is required for Basophil differentiation
IL-4
What cytokine is required for Neutrophil differentiation?
G-CSF
What cytokine is required for Eosinophil differentiation?
IL-5
What cytokine is required for lymphoid differentiation?
IL-7
What cytokine is required for T cell differentiation?
IL-2
What cytokine is required for B cell differentiation?
IL-3
What cytokine is required for monocyte differentiation?
GM-CSF, M-CSF
What is unique about the myeloid family? (are they innate or adaptive?)
ALL THE CELLS OF THE MYELOID LINEAGE ARE INNATE
Describe a myeloid lymphocyte
Comprise most of the innate immune system
First line of defense against a microbial infection
Responsible for presentation of antigen to the adaptive immune system
They are effector cells that can propagate or regulate an established immune response
What is the function of Neutrophils?
Phagocytosis and activation of bactericidal mechanisms
Describe the mechanism of phagocytosis
A pathogen binds to a receptor on a macrophage or neutrophil, which then releases cytokines and inflammatory mediators
The phagocyte then engulfs the pathogen and internalizes it in a phagosome
The phagosome is acidified and fuses with a lysosome
The phagolysosome is filled with antimicrobial enzymes, and the pathogen is degraded (and displayed in the case of APCs)
In addition to phagolysosome formation, what else do Neutrophils do?
release granules of other antimicrobial substances
Primary Granules (azurophilic): Direct toxic/enzymatic activity
Secondary granules (specific): free radical formation
Where are neutrophils generally found, and are they short lived or long-lived?
Neutrophils are most often found in the blood (>70% of WBCs in the blood) but can extravasate into tissues if infected
Short lived –> generally will apoptose after one round of phagocytosis, death can help wall off an infection
In addition to phagocytosis and granule release, how else can neutrophils kill invaders?
NETs (neutrophil extracellular traps)
What are the general functions of Macrophages/Monocytes?
Phagocytosis and activation of bactericidal mechanisms
Antigen presentation
How do macrophages recognize foreign stuff? Is it specific?
Macrophages are innate, so not specific, but have receptors such as TLRs, LPS receptors(CD14), Mannose receptors, glucan receptors, scavengar receptors that help them recognize foreign stuff
What is the general function of dendritic cells?
Antigen uptake in peripheral sites and antigen presentation to naive T cells
Describe the process of a dendritic cell presenting Ag to a T cell
The dendritic cell will recognize a pathogen, phago- or pinocytose it, migrate to a lymph node, and present it to a T cell
What are the general functions of an eosinophil and where are they found?
Killing of Ab coated parasites via granule release
Found in sub-epithelial connective tissue
What are the components of eosinophil granules and what are their functions?
Major basic protein: toxic, stimulate histamine release from mast cells
Eosinophil collagenase: remodels connective tissue matrix
Leukotrienes: smooth muscle contraction, vascular permeability, increased mucus secretion
Eosinophil-derived neurotoxin: helps paralyze pathogen
Are eosinophils involved in allergic response?
Yes - can help sustain allergic reactions, chronically can lead to tissue remodeling
What are the general functions of mast cells?
Release granules containing histamine and active agents - the “doorkeepers” allowing other cells to come to the site of infection and do their job
have basophilic granules rich in histamine and heparin
Where are mast cells found?
vascularized connective tissue below the epithelium
What are the general functions of Basophils?
immunity against parasites
participates in immune response
have basic granules like mast cells
What are the general characteristics of the lymphoid cell?
Includes innate NK cells and adaptive lymphocytes
Generated in primary lymphoid organs: T cells in the thymus, and B cells in the bone marrow (along wth NK cells)
Circulate in the blood and often stop off at secondary lymphoid organs (lymph nodes, spleen, mucosal lymphoid tissue)
What are the general functions of a NK cell?
Recognize cells that don’t look right: release lytic granules that kill some virally infected cells and tumors
Contain viral infections while T cells expand
induce apoptosis
Are NK cells innate or adaptive?
They are INNATE! Their genetics do not change
What are the general functions of naive lymphocytes?
will differentiate into an effector B cell (plasma cell) or effector T cell
gives lasting immunological immunity
What are the characteristics of a B cell?
Have surface B cell receptors that are variant
recognize a specific antigen
proliferate and differentiate into plasma cells upon recognition of Ag
What are the characteristics of a plasma cell?
Effector form of B cell that produces Ab against a specific Ag
What are the characteristics of a T cell?
Commander in Chief - variant receptors, will proliferate and differentiate after encounter with Ag
Cytotoxic T cells: like NK cells (but slower to action) directly kill infected cells
Helper T cells: orchestrate antibody and macrophage responses
