Quiz, old exams, study Qs Flashcards
How does the immune system recognize the presence of foreign microorganisms?
The innate immune system recognizes PAMPs on foreign microorganisms with their PRRs (NLRs & TLRs). The adaptive immune system recognize antigens that has been presented to them by APCs
What are key characteristics of the innate immune system, and which are its key components?
Fast, non-specific, no memory. Key components include macrophages, dendritic cells, ILCs, complement system and granulocytes.
What is the role of the complement system?
To recruit phagosomes, create MACs, and cause phagocytosis.
How can the complement be activated?
1) Lectin pathway, by binding of complement proteins to carbohydrates on the pathogen surface.
2) Classical pathway, by binding of complement proteins to Fc regions on bound antibodies.
3) Alternative pathway, by spontaneous hydrolysis of complement protein
What cells are APCs?
DCs, macrophages, B-cells
What are the main function of antigen presenting cells?
To present antigens to naive T-cells, causing activation
What are the functions of the granulocytes?
To help fight infections in the body
Why are granulocytes called granulocytes?
Because they have cytoplasmic granules
What is stored in the cytoplasmic granules of granulocytes?
AMPs such as defensin, histamine, lysozyme, prostaglandins, cathepsin
Which are the primary and secondary lymphoid organs and what is the function of these organs?
The primary lymphoid organs are where lymphoids are produced and mature; these are the thymus and the bone marrow. The secondary organs are where they are stored until activated; this includes the spleen, lymph nodes and peyers patches.
How do immune cells find their way to a site of inflammation?
Epithelial cells, and macrophages, release chemokines that attract the immune cells with the right receptors
What do lymphoid cells do and how many different types exist in humans?
Lymphoid cells are responsible for the adaptive immune system. There are two in humans, T- and B-cells.
How do lymphocytes generate variability in their antigen receptors and how many such receptor types exist in humans?
They have variable changes with regions of hypervariability, especially in the CDR regions. Furthermore, both heavy and light chain are combined by V(D)J gene segments, which can be combined in multiple different ways. There are also junctional diversity, where nucleotides are added in the junctions of the V-D-J gene segments during recombination.
What is a follicle and what takes place in a germinal center?
A follicle is the place in the lymph node cortex where naive B-cells sit. Germinal centers contain activated B-cells, that are going through clonal expansion and affinity maturation.
What immunoglobulin classes do humans have?
IgM, IgD, IgG, IgE, IgA
What effector functions do antibodies have?
They can neutralize the pathogen by binding to it and physically stop its function. It can also opsonize. The Fc regions on antibodies can recruit macrophages, and activate complement system.
Which part of the antibody is associated with the effector function?
The variable region, which binds to the antigen.
Which signals are needed to activate a T-cell?
First signal via binding of the TCR + CD4/8 to MHC Class I/II. Second signal via binding of CD28 to B7/CD80.
How are antigen loaded on MHC Class I?
Via the endogenous pathway. Proteins are ubiqunated and broken down by proteosome, then transported into ER lumen by TAP and loaded to MHC Class I
How are antigen loaded on MHC Class II?
Via exogenous pathway. Pathogen is taken up by endocytosis, broken down and transported to ER lumen. MHC Class II has invariant chain that stabilize them that is removed by CLIP; then antigen can be loaded and antigen:MHC complex transported to cell surface.
How can a cytotoxic T-cell recognize and kill an infected host cell?
Almost all cells have MHC Class I receptors that present what’s inside the cell. If one presents the T-cells antigen, it will release granules containing perforin, granzymes, and serglycin. Perforin transport granzyme into the infected cell, where it can kill it.
Which cytokines stimulate cellular immunity?
IL-12, IFN-γ
Which cytokines stimulate proliferation of lymphocytes?
IL-2
Which cytokine stimulate macrophages?
IFN-γ
Which cytokines stimulate immune suppression?
IL-10, TGF-β
What cytokine inhibits viral replication?
IFN-α
Which innate cells are present in the skin and ready to respond to microbes?
Langerhans cells, intraepithelial T-lymphocytes
What do mast cells granules contain?
Protease, histamine, heparin
Describe MHC Class I
One membrane bound region.
What are the characteristics of innate type of B cells?
They produce natural antibodies (IgM)
Which immunoglobulin has the capacity to be transferred across epithelial cells by a specific receptor mediated mechanism?
IgA
Name two things that basophil granules contain
Histamine and proteoglycans (heparin)
Name four things that mast cell granules contain
Histamine, proteoglycans, proteases, cytokines
In which reaction is basophils involved?
Allergic reactions, due to their FcεR
Name two things that eosinophil granules contain
RNase and DNase, lipase
In which reaction is eosinophils involved?
Against parasitic infections
Name two things that the neutrophil granule contain
Lysozyme, defensins
In which reaction is neutrophils involved
Against extracellular bacteria
Name two strategies for NK mediated killing and how they work
Missing self recognition - MHC Class I is a inhibitory receptor for NK cells, and cancer and virus might downregulate it to escape immune recognition. This will activate the NK cell.
ADCC - NK cells recognize the bound IgG Fc region (FcγRIII) or Fas, and release cytotoxic agents. Fas cause apoptosis
