Immune System & Autoimmunity Flashcards
Innate vs Adaptive Immunity
Innate - fast response, nonspecific resistance, recognize PAMPs through TLRs, and foreign substances
Adaptive - slow but long lasting, specific resistance - forms antibodies, triggered by cytokines. T and B cells
What are macrophages called in different parts of the body?
Alveolar (lungs)
Kupffler cells (liver)
Microglial cells (brain)
Osteoclasts (bone)
Histiocytes (connective tissue)
Function of macrophages
Engulf pathogens
Function of NK cells
- Recognize abnormal cells due to decreased MHC-I molecule (or other molecule that normal cells have) as a “non self”
- Release perforins and granzymes to kill the cell
What do leukocytes start off as?
Hematopoietic stem cells in the yolk sac and bone marrow of fetus
Myeloid progenitors become:
RBCs
Platelets
WBCs (neutro, baso/mast cells, eosino, monocytes/macrophages, eosino, dendritic cells)
Develop in bone marrow
Lymphoid progenitors become:
Lymphocytes (T and B cells, NK cells)
Thymus and bone marrow (for B and NK)
Neutrophil function
Phagocytosis
Also has enzymes and microbial properties like lactoferrin (steals iron from pathogens)
First cells to inflammation site
Basophils (in fluids)
Mast cells (in tissue)
Function
Allergic reactions and parasites
Granules contain histamine & heparin
Histamine dilates blood vessels so there’s redness at allergic reaction site
Eosinophil function
Has toxic compounds that damage parasite cell membrane
Some phagocytic activity
Neutralizes mast cell products
What are the granulocytes?
Neutrophils
Basophils
Eosinophils
Agranulocytes
Monocytes
Lymphocytes
Monocyte function
Matures into macrophages
Phagocytic
Antigen presenting cell to lymphocytes
Produces pro inflammatory cytokines, which attract neutrophils to infection site —> activates NK and T cell differentiation and increases vasodilation to bring more cells and blood to flow
Dendritic cell function
Phagocytes
Langerhan cells: specialized dendritic cells that are the most effective APCs (class II MHC - present to T helper cells)
Activate T cells
CR1 (CD35) present on:
(CR1 is the receptor for C3b (which is attached to bacteria))
- RBCs
- WBCs (Neutrophils, Monocytes/Macrophages, Eosinophils, B & T cells)
- Follicular dendritic cells
Basically any phagocytic cell
C3b surrounds bacteria and attaches to CR1, then phagocytizes the bacteria
Which cells have TLRs?
- Endothelial cells
- Dendritic cells
- Plasmacytoid dendritic cells
- NK cells
- WBCs (neutrophils, macrophages, B and T cells)
TLRs function
Detect PAMPs on pathogens
First responder to infection
Translocation of transcription factors, cytokine modulation, interferon-stimulated gene regulation (for inflammatory response or antimicrobial release)
Interferon
Works against viruses
Protein cytokines trigger:
- Macrophage activation (gamma IFN)
- substances that interfere with RNA viral reproduction (alpha and beta IFN)
Which cells help with worm infections?
Eosinophils (parasites)
IgE (worm infection) associated with mast cells & basophils
Cells that help with phagocytosis
Macrophages/monocytes
Neutrophils
Dendritic cells
Eosinophils have some phagocytic activity
Complement pathways and their convertase
- Classical pathway: C4bC2a Classical C3 convertase
- Alternative pathway: C3bBb convertase
- Lectin pathway: C4bC2a Classical C3 convertase
Classical Pathway (3rd to act)
- C1 binds to IgM
- C1 + IgM act on C2 and C4 complement proteins
- this cleaves to C4b and C2a, which helps to cleave C3 —> C3a and C3b
- C3a: causes inflammation
- C3b: tags the pathogen for CR1 phagocytosis or C5-9 lysis of pathogen
Alternative pathway
Factor B and D and Properdin (helps stabilize convertase) - unique to this pathway
LPS is most potent
Slower than classical
C3bBb convertase