| what are the cells of the adaptive immune system? | T lymphocytes, B lymphocytes, (dendritic cells) |
| how can the T lymphocytes be classified? | they are distinguished by their CD4 and CD8 coreceptors.
naive lymphocytes are not active yet, when they're activated they become effector lymphocytes or memory lymphocytes |
| how can the B lymphocytes be classified? | naive B lymphocytes are not active yet, when they are activated they become effector cells called plasma cells or memory cells |
| what is the MHC and what are the differences between the two classes? | the MHC is the major histocompatibility complex which are membrane molecules that are present on certain cells.
class I is present on all host cells, when these cells get infected they present the antigen on these molecules. class I mostly presents antigens to CD8 T cells. they present intracellular antigens
class II is only present on antigen-presenting cells and presents antigens to CD4 T cells. they present extracellular antigens |
| what are the three types of dendritic cells and what are their functions? | follicular DCs: present in the B cell region of lymph nodes and spleen, do not process antigens but display them to B cells.
plasmacytoid DCs: present in the blood and present antigens to T cells
myeloid DCs: professional APCs that present antigens to T cells and produce cytokines |
| how do dendritic cells form the bridge between the innate and adaptive immune system? | they take up debris and proteins at the site of infection. when they are activated by PAMPs or DAMPs, they release acute-phase cytokines which make them mature.
mature DCs cannot take up anything anymore, they move to the lymph nodes. there they upregulate MHC II and present antigens on them and they upregulate CD80, CD86 and CD40 which activate T cells |
| what are CD8 T cells and what is their function? | the CD8 T cells are the T cells that contain CD8 coreceptors
their function is to attach to and kill infected cells by releasing granzymes and perforin |
| what is cross presentation? | it is the process in which dendritic cells first take up infected host cells, tumor cells, microbes and microbial and tumor antigens.
the ingested antigens are then transported into the cytosol, where they are processed by the proteasome.
antigenic peptides are then generated in the ER and bind to class II MHC molecules.
this is an exception because the dendritic cells can present the intracellular antigens of another cell on its own MHC-II proteins to activate T cells.
the function of this is that CD4 T cells can be activated. |
| what are CD4 T cells and what is their function? | CD4 T cells are T cells that contain the CD4 coreceptor. they function as helper T cells of the immune system
they interact with the antigens on the MHC II molecules, leading to the production of antibodies and helping the phagocytosis. |
| what are the functions of TH10, TFH and Treg cells? | TH10: produce a generic response by making cytokines
Follicular helper T cells: promote production of antibodies
Regulatory T cells e.g. Treg cells: antigen-specific suppressor cells |
| how are the CD4 T cells activated? | CD4 T cells need two signals to become activated;
1. the interaction of the T cell receptor with the antigen on the class II MHC molecules on the APC
2. co-stimulatory signal; binding of B7 molecules on the APC to the CD28 molecules on the T cell
when the CD4 T cells are activated they leave the lymph node and go into the blood stream to go to the B cell zones of the lymph node and spleen |
| how do CD8 T cells work? | when it comes across an infected cell, it forms an immune synapse between itself and the target cell. through this synapse granules containing granzymes, perforin and other toxins are released.
perforin makes little holes in the cell membrane of the target cell, which enables granzymes to enter. the serine protease of the granzymes then triggers the caspase cascade of the cell, inducing apoptosis |
| what cytokines activate TH17 cells? What transcription factors are involved in the activation? | activate: IL-1, IL-6, IL-23, TGF-beta from dendritic cells
transcription factors; ROR-gamma-t, STAT3 |
| what cytokines activate TH1 cells? What transcription factors are involved in the activation? | activate: IL-12 from dendritic cells and IFN-gamma from NK cells
transcription factors: T-bet, STAT4, STAT1 |
| what cytokines activate TH2 cells? What transcription factors are involved in the activation? | activate: IL-4 from mast cells and eosinophils
transcription factors: GATA-3, STAT6 |
| what is the function of TH17 and what cytokines are involved? | fighting initial antibacterial and antifungal responses
IL-17: antimicrobial peptides and inflammation neutrophil response
IL-22: antimicrobial peptides and increased barrier integrity |
| what is the function of TH1 and what cytokines are involved? | IFN-gamma: classical macrophage activation, enhancing microbial killing |
| what is the function of TH2 and what cytokines are involved? | IL-4: antibody production, leading to mast cell degranulation
IL-4, IL-13: intestinal mucus secretion, peristalsis and alternative macrophage activation (enhanced tissue repair)
IL-5: eosinophil activation |
