Intro to Immune System Flashcards
What are the 2 elements of the immune system
Fixed: lymphoid organs (primary:brain/thymus, secondary: spleen/lymph nodes/mucosal immune tissue)
Mobile: immune cells and soluble humoral components (antibodies, complement, and acute phase proteins)
What cells are part of innate immunity
Epithelial barriers Phagocytes Dendritic cells Complement NK cells ILCs
“PED-INC”
What cells are part of adaptive immunity
B lymphocytes
T lymphocytes
“BAT” B-lymph adaptive T-lymph
What cells does +G-CSF (granulocyte colony-stimulating factor) give rise to?
Basophils
Eosinophils
Neutrophils
occurs in bonemarrow
“BEN comes from the myeloid community and lives on +G-CSF street”
What cells does +M-CSF (monocyte colony-stimulating factor) give rise to?
Monocytes
Dendritic cells
occurs in bonemarrow
“Mary the MD comes from the myeloid community and lived on +M-CSF street”
What cells does +IL-7 (interleukin-7) give rise to?
B-lymphocytes & T-lymphocytes
“BiL & TiL come from the lymphoid family and they live on +IL-7 street”
what can a hematopoietic stem cell give rise to
HPCs are multipotent stem cells that give rise to myeloid and lymphoid progenitors
what can monocytes do
They can migrate into tissues and differentiate into monocyte-derived dendritic cells and tissue macrophages
What influences T-cell precursors to differentiate into functional T cells
Locally produced cytokines and growth factors
What cells make up the absolute white blood cell count
Neutrophils Eosinophils Basophils Monocytes Lymphocytes (B&T)
which leukocytes are phagocytes
Monocytes and Neutrophils
What kind of lab exam provides the “complete hematologic picture” from a MORPHOLOGIC standpoint
CBC w/ differential (CBC w/ a differential leukocyte count)
Can we see anything on a blood smear?
If we stain the leukocytes with Giemsa stain. Otherwise, the cells are basically transparent, too pale, and almost invisible.
A blood smear does not allow differential of what kind of cells
B cells
T cells
NK cells
They all look the same under a microscope! To see them, we use antibodies that recognize specific antigens, termed CDs (cluster of differentiation) that are selectively expressed on each type of leukocyte
What are CD molecules and why do we use them
They are cell surface markers. Useful for identification and characterization of leukocytes.
What are T-cell markers
CD3
CD4
CD8
What are B-cell markers
CD19
CD20
What are NK-cell markers
CD56
What are macrophage/monocyte markers
CD14
Steps of a functional phagocyte response
- Recruitment of the cells to the infection site
- Recognition and activation by microbes
- Microbes ingested by phagocytosis
- Ingested microbes are destroyed
What do activated phagocytes secrete
Cytokines which promote and regulate immune responses
Which cell mediates the earliest phases of inflammatory reactions
Neutrophils (note: neutrophils are phagocytes)
What kinds of inflammatory mediators are produced by neutrophils
Cytokines
Prostaglandins
Leukotrienes
“CPL by neutrophiiiils” rhyme
What is leukocytosis
Elevated WBC. Neutrophilia is the most common type of leukocytosis because neutrophils are the most common granulocyte in blood circ.
What causes a “left shift”
Left shift is seen during infection or inflammation. Bone marrow is producing more WBCs and releasing them into the blood before they are completely matured.
What is leukopenia
Decreased WBC. Also called agranulocytosis or granulocytopenia. Often caused by chemo or radiation. Severe neutropenia increases risk of infection. Suspect neutropenia in people who have frequent or unusual infections.
How can a neutrophil kill bacteria
Neutrophils are phagocytes and can kill bacteria by:
- Phagocytosis
- Degranulation
- NETs (neutrophil extracellular traps)
How are pathogens in phagosomes, such as neutrophils, killed?
Reactive oxygen species or antibacterial proteins (cathepsins, defensins, lactoferrin, lysozyme)
What are NETs ( neutrophil extracellular traps) composed of
Core DNA element to which histones, proteins, and enzymes that are released from a neutrophil are attached
How do NETs work
Thought to kill w/ antimicrobial histones and proteases
Differentiate between monocytes and macrophages
Monocytes are phagocytes in the blood and macrophages are in the tissues
What’s unique about the lifespan of monocytes
Monocytes can have prolonged survival during inflammation and apoptosis and inflammation improves
What is monocytosis
Increased number of monocytes in the blood. Results from chronic infection, autoimmune disorders, certain cancers, sarcoidosis (proliferation of macrophages in tissues)
What is monocytopenia
A low number of monocytes in the blood. Can occur in people receiving chemo.
What do inflammatory macrophages do in tissues?
- Carry out inflammatory reactions
2. Tissue remodeling (“repair” damage produced by hypersensitivity reactions)
What KIND of cell is a dendritic cell (DC)
An antigen-presenting cell (APC). Note: DC is part of innate immunity
What are 2 types of DCs?
- Myeloid (mDC)
2. Plasmacytoid (pDCs)
Where are mDCs derived from?
mDCs are derived from monocytes similar to tissue macrophages.
What do mDCs do?
They capture, process, and present their surface antigens to T-cells.
pDCs are a subset of what kind of cells?
pDCs are a subset of IFN-producing (interferon producing) DCs that circulate through the blood and peripheral tissues
What is an important subset of DCs?
Langerhans cells. LCs reside in the epidermis and after Ag-dependent activation they become potent APCs (acute phase proteins)
Which cells are considered granulocytes
Neutrophils Eosinophils Basophils Tissue eosinophils Mast cells
Which 3 cells play a key role in allergic reactions
Mast cells
Basophils
Eosinophils
Mast cells and basophils contain granules filled with:
- Histamine, serotonin, heparin
- Cytokines and chemokines
What are sentinel cells
“Sentinel cells refer to cells in the body’s first line of defense, which embed themselves in tissues such as skin. Sentinel cells can refer to specific antigen-presenting cells, such as: Macrophages. Kupffer cells - in the liver. Langerhans cells - in the skin and mucosa (*these are a form of dendritic cells)”
What is mastocytosis
Pathologic increase in mast cells within tissues. Due to histamine release, may have itching, hives, anaphylactic shock.
What is the most prominent feature of eosinophils
They have large secondary granules containing 4 basic proteins. Basic proteins are involved in anti-parasitic defense as toxins directed against helminths.
Where do NK cells reside
In the blood and in the tissue. “NK knows no bounds”
where are NK cells generated from?
NK cells come from the lymphoid progenitor cells in the bone marrow. The lymphoid progenitor creates a T-cell precursor which goes on to make NK cells.
How do NK cells function?
Immune surveillance (purges body of infected cells and precancerous cells)
Where do NK cells undergo differentiation
Via precursor NK cells in the bone marrow
Do NK cell receptors have antigen specificity?
NO
Do NK cells generate immunologic memory?
NO
What do NK cells recognize?
They recognize antigens present on normal host cells. Can differentiate between self and nonself. The absence of an Ag is what activates NK cells. Broad specificity.
What are the 2 major types of lymphocytes
T-cell lymphocyte
B-cell lymphocyte
Where do T-cells develop and mature
In the thymus. When a mature T-cell lymphocyte is Ag-stimulated, it gives rise to the development of cell-mediated immunity
Where do B-cells develop and mature
In the bone marrow and spleen. When a B-cell is activated it leads to humoral immunity, an immunity that involves the production of soluble effector molecules (immunoglobulins AKA Abs )
What is the function of CMI (cell-mediated immunity)
To kill infected HOST cells which thereby eliminates the reservoirs of infection
What do T helper cells do
They help B-cells maker higher affinity immunoglobulins (abs)…contributing to the eradication of extracellular microbes
How is CMI and intracellular microbes related?
CMI mediates the host defense against intracellular microbes, like viruses and bacteria, that are inaccessible to circulating Abs ( from B-cells)
What is the function of humoral immunity?
Block infections and eliminate extracellular microbes (involves B-lymphocyte)
What are the 2 functions of cell-mediated immunity
- Activate macrophages to kill phagocytosed microbes (involves helper T cells)
- Kill infected cells and eliminate infection reservoirs (involves cytotoxic T lymphocyte)
Explain the clonal selection hypothesis
We have many distinct lymphocytes specific for different antigens. When the lymphocyte with receptors for a certain Ag seeks and binds to it, the cells are triggered to proliferate and differentiate giving rise to clones of cells that are specific for whatever type of Ag it is. Links to memory involved in adaptive immunity.
