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immunology
immunology questions
| Question | Answer |
|---|---|
| what are the chemicals released by the thymus | thymosin thymotaxin thmopoetin thymic factors |
| what do the chemicals released by the thymus do | chemotaxis of t cell precursor |
| what are the enzymes produced by the precursor t cell after the action of thymic chemicals | precursor t cells produce the enzymes RAG1 and RAG2 |
| what is the function of RAG1 and RAG2 | they shuffle the DNA to produce TCR |
| what is the second important thing thymic chemicals induce in t cell precursor after tcr | they help the expression of cluster differentiation proteins or CD proteins |
| what are the types of CD proteins | there are two types of CD proteins which are CD4 and CD8 |
| with wich MHC does the cofactor CD4+ interact with | it's MHC2 |
| WITH WHICH MHC does the cofactor CD8+ interact with | it's MHC1 |
| what is the positive selection of t lymphocytes | the positive selection of t lymphocytes is when the CD4 and CD8 interact with the thymic MHC1,2 and recognize them perfectly |
| what are the primary lymphoid organs | bone marrow thymus |
| what are the peripheral(secondary) lymphoid organs | lymph nodes spleen mucosal associated lymphoid tissue(MALT) Gut-associated lymphoid tissue(GALT) |
| which process happens in primary lymphoid organs | lymphopoisis |
| what are the functions of the bone marrow | rise of hematopoietic stem cells developement of b lymphocytes giving rise to other lymphoid progenitors migrating to T lymphocytes |
| what is special about the bone marrow(about its type ) | bone marrow is both a primary and a secondary lymphoid organ |
| where is the thymus located | the thymus is located: below the thyroid gland behind the top of the sternum |
| how is the thymus made | the thymus is a parapharyngeal derivative arising from the epithelial of the third and fourth pharyngeal pouches |
| which process happens in the secondary lymphoid organs | in the secondary lymphoid organs lymphocytes are exposed to the antigen and they produce antibodies |
| what are the three regions of lymph nodes | outer cortex(B lymphocytes) middle paracortex(T lymphocytes inner medulla(both) |
| function of lymph nodes | initiation and development of humoral and cell mediated immune responses |
| what does the interaction between B7(b cells) and CD28(t cells ) induce | it induces the production of cytokines responsible for B cell |
| which T cells can survive | tcr must recognize MHC |
| what happens in the medulla for T cell development | T cells interact with the MHC or self peptides |
| what are the exceptions for immature b cells that interact with the self antigens | cells that need more than one receptor become anergic cells with low affinity (non-cross linking self molecules ) the become |
| what is the tcr composed of | tcr is composed of alpha and beta chains ,named ab-TCR |
| which chain of tcr is arranged first | beta chain then alpha chain |
| how does the activation of t cells occur | first interation :antigen +TCR but the interaction is not very strong so we need another cofactor cd4 that stabilizes the interaction then it induces a signal via the zeta chain but all that is not enough so we need another coreceptor Ig(Independent) |
| when can t cells recognize the antigens | if it's only presented on cell surface |
| what is MHC complex | it's a glycoprotein |
| what is human MHC called | human MHC is called HLA |
| what is the function of MHC | present antigen to t cells |
| what are the characteristics of MHC | It's polygenic and polymorphic |
| What is the difference between MHC1 and MHC2 | MHC1 has alpha 1,2,3 and beta microglobulin MHC2 has alpha1,2 and beta1,2 |
| which cells express MHC2 | macrophages dendritic cells B cells |
| which cell doesn't have a nucleus but express MHC1 | they are platelets |
| do APC express MHC1 | yes ,they have MHC1 and MHC2 |
| what is antigen processing | it's the proteolytic cleavage of proteins by enzymes (proteases)into small fragments(antigen peptides) |
| what is antigen presentation | presentation of antigen fragments by MHC2 |
| where are endogenous antigens processed | endogenous antigens are processed in the cytosol |
| where are exogenous antigens processed | they are processed in the endosomes |
| what is the pathway of endogenous antigens (for apc) | phagosome cytosol proteasome ER (where MHC2is produced) GA vesicle enchored in the cell membrane |
| what is the pathway of the endogenous antigens for a normal cell | cytosol proteasome(for degradation) ER(where MHC1 is synthesized) GA vesicles anchored in the cell membrane |
| what is the pathway of exogenous antigens | extracellular matrix phagosome phagolysosome MHC2 +invariant chain in ER which becomes MHC2+CLIP fuses with peptide epitope in the phagolysosome the new complex is transported to cell membrane |
| What is the function of the TAP transporter | is responsible for transporting the peptide from cytosol to RER |
| which HLA regions encode for MHC1 | HLA- A, -B, and –C |
| which HLA regions encode for MHC2 | HLA-D(R,P, and Q) |
| which proteins does MHC1 interact with | endogenous proteins |
| which proteins does MHC2 interact with | exogenous proteins |
| what are types of endogenous proteins | proteins produced inside the cell altered self protein antigens(tumor antigens) non-self protein antigens (viral proteins,intracellular bacterial proteins) |
| what are types of exogenous proteins | proteins produced outside the cell(bacterial,viral,fungal,parasitic Ags) |
| which structure recognizes the complex(MHC1+ processed Ag) | It's the complementary shaped TCR/CD8 on the surface of a CTL |
| what is the function of invariant chain | the invariant chain binds to the groove of the MHC2 to prevent peptides designated to bind to MHC1 within the ER from binding to MHC2 |
| what does the complex MHC2+invariant chain becomes in the GA | The invariant chain got degraded and it becomes clip and therefore the complex bocomes MHC2+CLIP |
| what is meant by croos presentation of an antigen | cross presentation of antigen is the process done by professional APCs which are able to present extracellular antigens(exogenous) to CD8+ T cells via the MHC class I pathway. |
| how are t cell antigens kept apart | Control is through accessory proteins • Class I requires TAP – Tapasin as control • Class II requires low pH for removal of Ii |
| what is meant by MHC restriction | is the inability of t cells to recognize an antigen unless it's a specific antigen presented on a specific MHC molecule |
| what are the characteristics of the pro b cell(b cell progenitor) | rearrangement of heavy chains expression of CD19 and CD45R that promote the expression of genes involved in the development of BCR |
| what are the characteristics of pre b cell | expression of IL7 receptor (promotes the survival and proliferation of B cells) rearrangement of the light chains Expression of mu heavy chains in association with Ig alpha-Ig beta heterodimer use of surrogate light chains stops VDJ and induce VJ |
| what are surrogate light chains | are composed of two proteins: VpreB and lambda5, and can pair with the heavy chain to form a pre-BCR complex. |
| what are the characteristics of immature b cell | IgM expression cells interact with self antigens for their negative selection |
| which immature b cells are able to become functional | immature b cell that do not interact with the self antigens |
| what are the characteristics of mature b cells | IgM and IgD are both expressed migrate outside of the bone marrow genes for Ig rearrangement are shut |
| what are the types of antigens that activate the immature b cells ? | the two types of the antigens are two: thymus dependent antigens (soluble proteins) thymus independent antigens (LPS,capsular polysaccharides) |
| what is the difference between the antigens activating the immature b cells | thymus independent antigens are not as strong as the thymus independent antigens and doesn't produce the memory cells ,and class switching doesn't occur |
| how many signals are needed to activate b cells | two signals are required in case of TI Ag the two signals are generated after the binding otherwise in the case of t helper involvement ine signal is generated by the Th cell(CD40,CD40L) and the other is generated by the antigen |
| which type of plasma cells are generated by the cytokine IFN gamma | IgG2a or IgG3 |
| which type of plasma cells are generated by the cytokine TGF-beta | IgA or IgG2b |
| which type of plasma cells are generated by the cytokine IL-4 | IgE or IgG1 |
| which type of plasma cells are generated by cytokines IL-4,IL-5 and IL-2 | IgM |
| what is the function of the cofactor C3D in the activation of b cells | C3d can bind to the processed antigen-BCR complex and act as a bridge between the BCR and co-stimulatory molecules on the surface of B cells. which is important for the high affinity binding and generation of memory cells |
| what are the proteins of the b cell coreceptor and what are their functions | there are three proteins called CD19,CD81,CD21. they create a signal amplification pathway that enhances BCR signaling. |
| what are the subsets of b cells | there are two subsets B1(fetal liver derived b cells)and B2(bone marrow derived b cells) |
| where are the B1 subset of b cells mostly found | the B1 subset of b cells is mostly found in the peritoneum,pleural cavity and mucosal tissue they produce natural antibodies and are characterized by the CD5 receptor |
| what do t cells precursors express on their cell surface | they present two important structures CD44 which is an adhesion molecule CD25 (Interleukin-2 receptor alpha chain) |
| site the difference between the DN t cells | DN1(CD44+,CD25-) DN2(CD44+,CD25+) DN3(CD44-,CD25+) DN4(CD44-,CD25-) |
| what are the DN that undergo a specific selection? and what is the name of that selection? | it's the DN3 t cells that undergo a process calle beta selection for cells that have successfully rearranged their TCR-b chain locus. |
| what happens to the beta chain of the DN3 t cells | b chain then pairs with the surrogate chain, pre-Ta, and produces a pre-TCR, which forms a complex with CD3 molecules |
| where does the positive selection of t cells occur? | positive selection occurs in the cortex of the thymus (cells that engage antigen/MHC with an appropriate affinity survive, whereas cells that interact with a weaker affinity die by apoptosis.) |
| where does the negative of t cells occur? | the negative selection of t cells occurs in the medulla |
| what happens after the negative selection of t cells | one of the coreceptors is dwonregulated to give raise to either naive CD4+ cells or naive CD+ cells |
| what is the result of positive selection | postive selection result in MHC restriction and only reactive thymocytes survive |
| give one difference between alpha,beta ; and gamma,lambda chains | Alpha and beta chains: recognize peptides presented by MHC class I or II molecules. Gamma and delta chains:present on a subset of T cells called gamma delta T cells, recognize non-peptide antigens(lipids)presented by NC MHC molecules |
| function of CD3 in mature t cells | CD3 is a coreceptor having different subunits(CD3γ, CD3δ, CD3ε, and CD3ζ),after getting phosphorylated by tcr, it transduces signals into the interior of the T cell, leading to T cell activation and proliferation |
| what is the first signal for the activation of f cells | it's the signal induced by the tcr receptor |
| who produces the second signal involved in t cell activation? | it's the complex formed by CD28R and B7 ligand presented |
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chaimaa
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