Specific Acquired Immunity Flashcards
What pathway is taken to display antigens on MHC Class I?
- Antigens are synthesized with in the cell
- Cell antigens of antigens from cell infections
What cell types express MHC Class I?
Expressed on all cells except RBCs. Lack of expression on RBCs may play a role in persistence of the malaria parasite, plasmodium
What T cell types interact with MHC Class I?
Recognized by CD8+ killer T cells
What is the result of T cell interaction with MHC Class I?
It surveys every cell in the body and makes sure it’s doing what it should be doing,
If CD8+ cell is activated:
-CD8+ cells expand/clone
-Daughter cell binds cell showing activation peptide
-T cell delivers lethal hit to that cell by signaling the target cell to commit suicide through apoptosis
-Target cell’s nucleus disintegrates and the cell dies
What pathway is taken to display antigens on MHC Class II?
Antigens are products of uptake from the environment and phagocytosis.
What cell types express MHC Class II?
Expressed on monocytes/macrophages, dendritic cells, B cells and epithelial cells of the thymus.
What T cell types interact with MHC Class II?
Recognized by CD4+ helper T cells.
What is the result of T cell interaction with MHC Class II?
Antibodies will be produced? B cell response?
What is is MHC known as?
HLA (human leukocyte antigens) - inherited in mendelian fashion - some from each parent
What are the common lymphocyte markers?
Antigen receptors & CDs
Which lymphocytes markers are expressed on T cells?
- TCR (alpha-beta or gamma-delta) - antigen receptor
- CD3 (part of TCR complex)
- Some have CD4, some have CD8, some have CD23
Which lymphocyte markers are expressed on B cells?
Immunoglobulin (Ig) - antigen receptor
- CD1
- CD19
- CD20
- CD23
- CD40
- CD79a (part of BCR complex)
- CD79b (part of BCR complex)
What are the five specialized subtypes of T helper cells?
Th1, Th2, Th17, Tfh, Treg (not helper: CTL)
What main cytokines drive a HSC to a lymphoid progenitor cell?
IL-7 and IL-3
What cytokines are general activators of T cells?
IL-2 and IL-15
What cytokines drive T helper cells to Th1 helper cells?
IL-12 and IFN-gamma
What cytokines drive T helper cells to Th2 helper cells?
IL-4
What cytokine down regulates Th1?
IL-10
What cytokines down-regulates both Th1 and Th2?
TGF-beta
Are T helper cells considered CD4+ or CD8+ T cells?
CD4+ T cells
-CD4+ increases their affinity for antigen and helps them get activated.
What do Th1 (helper) cells do?
- Recognize antigen and make a lymphokine that attracts thousands of macrophages (heavy duty phagocytes) to area where antigen has been recognized.
- This intense inflammation can wipe out a serious infection (or a transplanted kidney)
What do Th2 (helper) cells do?
- Stimulated macrophages to become ‘alternatively activated’, able to function in walling-off pathogens and promoting healing, a process that usually takes place after the pathogen-killing Th1 response.
- They are very important in parasite immunity
What do Th17 cells do?
- Similar to Th1 in that their main role is to cause focused inflammation
- More powerful than Th1
- Have been implicated in many serious forms of autoimmunity
What do Tfh (follicular helper) cells do?
- Stimulated by antigen and migrate from T cell areas of lymph nodes into the B cell follicles
- In B cell follicles, they help B cells get activated and make IgM, IgG, IgE and IgA antibody subclasses.
What do Treg (regulatory) cells do?
- Make cytokines that suppress the activation and function of Th1, Th17 and Th2 cells
- They keep the immune response in check
What do CTL (cytotoxic/killer T cells) do?
-Destroy any body cell they identify as bearing a foreign or abnormal antigen on its surface
How are target cells recognized for CTL cells?
- They examine surfaces of incoming dendritic cells for presented antigen fragments.
- In this case, they are looking for fragments on a different class of antigen-presenting molecule, called MHC Class I, which is not only on dendritic cells, but on ALL cells except RBCs
What is the general mode of action that killer T cells use to kill target cells?
- If activated, a clone of the CD8+ T cells gets expanded and the daughters circulate in large numbers throughout the body
- When one of the daughters of a stimulated CD8+ T cell binds a cell showing its “activation” peptide, the T cell delivers a lethal hit to that cell by signaling the target cell to commit suicide through apoptosis.
- The target cell’s nucleus disintegrates and the cell dies.
- The activated killer T cells then is free to find more targets. This is a great way to eliminate infected cells.
What are five common B cell disorders?
- X-linked agammaglobulinemia
- CD40 ligand deficiency
- Activation-Induced Cytidine Deaminase Deficiency
- Common variable immunodeficiency
- Omenn Syndrome
What are the five common T cels disorders?
- X-linked severe combined immunodeficiency
- Omenn syndrome
- DiGeorge syndrome
- Hemophagocytic lymphohistiocytosis
- IPEX
What causes X-linked agammagglobulinemia?
An absence of B lymphocytes
What causes CD40 ligand deficiency?
Failure of immunoglobulin class switching
What causes activation-induced cytidine deaminase deficiency?
-Failure of immunoglobulin class switching
What causes common variable immunodeficiency?
A failure to produce antibodies against particular antigens
What causes Omenn syndrome?
- VDJ recombination failure.
- Cannot produce BCRs or TCRs
What causes X-linked severe combined immunodeficiency?
A failure to produce mature T lymphocytes
What causes DiGeorge Syndrome?
Failure of the thymus to develop correctly
What causes hemophagocytic lymphohistiocytosis?
Failure of CD8+ T cells and NK cells to produce and/or release lytic granules
What causes IPEX?
A failure of peripheral tolerance due to defective regulatory T cells
