Immunology: Tcrs, Cytokines, Immunity Reactions At The Cellular Level

The TCR B locus contains V-D-J segments similar to the IgH locus, while the TCR alpha locus contains V-J segments like the Ig light chain loci. This suggests that the TCR B locus undergoes somatic mutation and contains diversity segments.

T cells cannot release their receptors and recognize antigens in their natural state. T cell receptors (TCRs) are membrane-bound proteins that are necessary for T cells to recognize antigens. The TCRs bind to antigens that are presented on the surface of antigen-presenting cells (APCs). This binding is essential for T cell activation and the initiation of an immune response. Therefore, T cells cannot release their receptors and still recognize antigens effectively.

The correct answer includes IL-2, IL-4, IL-5, IL-13, IFN-G, TNF-B, and TGF-B. These cytokines are involved in acquired immunity, which is the immune response that develops after exposure to a specific pathogen. IL-2 is important for the proliferation of T cells, IL-4 and IL-13 are involved in the activation of B cells and antibody production, IL-5 is involved in the activation of eosinophils and the production of antibodies, IFN-G is involved in the activation of macrophages and cytotoxic T cells, TNF-B is involved in inflammation and immune regulation, and TGF-B is involved in immune regulation and tissue repair.

Th1 cells are a subset of T helper cells that play a crucial role in cell-mediated immunity. They are known to produce specific cytokines that are involved in the immune response. The signature cytokines produced by Th1 cells are IFN-G (interferon-gamma) and sometimes IL-2 (interleukin-2). These cytokines are important for activating macrophages, promoting inflammation, and enhancing the cytotoxic activity of T cells. IL-10 and TNF-A are not typically produced by Th1 cells, making IFN-G and sometimes IL-2 the correct answer.

The correct answer is CXC because IL-8 belongs to the CXC chemokine family. CXC chemokines are characterized by the presence of a conserved amino acid motif, CXC, near their N-terminus. This motif indicates that there are two cysteine amino acids separated by another amino acid. IL-8 is a chemokine that plays a crucial role in inflammation and immune response by attracting and activating neutrophils to the site of infection or injury.

Granzyme is a type of enzyme that plays a role in inducing apoptosis, which is programmed cell death. It does this by cleaving and activating caspases, which are enzymes that initiate the process of cell death. This mechanism is an important defense mechanism of the immune system to eliminate infected or damaged cells. The other options listed do not accurately describe the function of granzyme.

Thymic epithelial cells, thymic dendritic cells, and thymic macrophages all play a role in mediating negative selection. Negative selection is a process in the thymus where developing T cells that recognize self-antigens too strongly are eliminated to prevent autoimmunity. Thymic epithelial cells present self-antigens to developing T cells, while thymic dendritic cells and thymic macrophages phagocytose and present self-antigens as well. Therefore, all three cell types are involved in the process of negative selection.

Macrophages, dendritic cells, and B cells are all examples of antigen-presenting cells (APCs). These cells play a crucial role in the immune response by capturing, processing, and presenting antigens to T cells. Macrophages are phagocytic cells that engulf and digest pathogens, presenting the antigens on their cell surface. Dendritic cells are specialized APCs that capture antigens in peripheral tissues and migrate to lymph nodes to activate T cells. B cells, on the other hand, present antigens to T cells after they have been internalized, processed, and presented on their cell surface. Overall, these cells are essential for initiating and coordinating an effective immune response.

Negative selection refers to the process in the thymus where T cells that recognize self-antigens are eliminated to prevent autoimmune reactions. The medulla of the thymus is the primary site for negative selection. This is where T cells that have high affinity for self-antigens presented by thymic epithelial cells are deleted through apoptosis. The medulla provides an environment rich in self-antigens and dendritic cells, allowing for the efficient removal of autoreactive T cells. Therefore, negative selection mainly occurs in the medulla of the thymus.

CD4+ T cells activate macrophages to kill ingested microbes that are able to survive in the vesicles of phagocytes. This response is important in defense against intracellular microbes. CD8+ T cells, on the other hand, kill cells that are harboring microbes in their cytoplasm, eliminating reservoirs of infection. Both types of T cell-mediated immune reactions play a crucial role in eliminating different types of microbes and contribute to the overall immune response against pathogens.

The statement "ALPHA AND DELTA TCRs HAVE D REGIONS" is false. T-cell receptors (TCRs) are proteins found on the surface of T cells and are responsible for recognizing antigens. While alpha and beta chains of TCRs do have D (diversity) regions, delta chains do not. Delta chains only have variable (V) and joining (J) regions. Therefore, the correct answer is false.

Positive selection occurs mainly in the cortex of the thymus. This is where T cells undergo a process called thymic education, where they are tested for their ability to recognize and respond to antigens presented by self-MHC molecules. T cells that recognize self-antigens too strongly or not at all undergo apoptosis, while those that recognize self-antigens with moderate affinity are positively selected to mature and leave the thymus. The cortex is the region of the thymus where this process primarily takes place.

The coligation of TCR with MHC/peptide and CTLA-4 with B7 leads to the arrest of the cell-cycle and termination of T-cell activation. This means that when these molecules bind together, it stops the T-cell from continuing its normal cell division and activation processes. This is an important regulatory mechanism in the immune system to prevent excessive T-cell activation and maintain immune homeostasis.

The thymus is roughly divided into two regions. This means that the thymus can be categorized into two distinct parts or areas.

Perforin is necessary for the delivery of granzymes into the cytoplasm. Granzymes are proteases that induce DNA fragmentation and apoptosis, leading to the death of target cells. Perforin forms pores in the target cell membrane, allowing granzymes to enter the cytoplasm and initiate cell death. This mechanism is primarily utilized by cytotoxic T lymphocytes (CTLs) to kill infected or abnormal cells.

Intracellular microbes can resist cell-mediated immune responses through various mechanisms. These include inhibiting phagolysosome fusion, which prevents the fusion of phagosomes with lysosomes, where microbes would typically be destroyed. They can also escape from the vesicles of phagocytes, allowing them to avoid destruction. Additionally, they can inhibit the assembly of class I MHC-peptide complexes, which are necessary for presenting antigens to cytotoxic T cells. Finally, they can produce inhibitory cytokines or decoy cytokine receptors, which can interfere with the immune response. These mechanisms help the microbes evade immune detection and destruction.

Macrophages are known to be the primary producers of chemokines. Chemokines are small signaling proteins that play a crucial role in immune responses by attracting immune cells to sites of infection or inflammation. Macrophages are immune cells that function as phagocytes, engulfing and destroying pathogens and cellular debris. They are widely distributed throughout the body and are capable of producing various immune molecules, including chemokines. Therefore, it is logical to conclude that macrophages are the molecules that produce chemokines mostly.

The correct answer is UNCOMMITTED PROGENITORS; CD44+CD25-CD4-CD8-. This answer is correct because during the DN1 phase of T cell development, the cells are considered uncommitted progenitors, meaning they have not yet committed to becoming T cells. Additionally, they are characterized by the cell surface markers CD44+CD25-CD4-CD8-. These markers help identify the specific stage of T cell development and distinguish them from other cell types.

CD4+ TH1 cells play a crucial role in recognizing antigens of microbes that have been ingested by macrophages. They express CD40 ligand and secrete IFN-gamma, which work together to activate macrophages. This activation stimulates defense against intracellular microbes. Additionally, CD4+ TH1 cells secrete cytokines and chemokines, leading to tissue repair once the infection is cleared. They also enhance antigen-presenting cell (APC) function by increasing the expression of class II MHC molecules and costimulators, promoting T cell activation. The infiltration of T cells and monocytes into tissues, along with increased vascular permeability, is caused by CD4+ T cells secreting cytokines, further activating macrophages.

T cell-mediated killing involves the activation of both TH cells and TC cells. TH cells, or helper T cells, play a crucial role in coordinating immune responses by activating other immune cells. TC cells, or cytotoxic T cells, directly kill infected or abnormal cells. Therefore, the correct answer is "a and b" because both TH cells and TC cells are involved in T cell-mediated killing. The other options, such as a calcium-dependent reaction or destruction of the T cell, are not accurate explanations for T cell-mediated killing.

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There are two subfamilies of chemokines.

IL-1 is also known as interleukin-1. Interleukins are a group of cytokines that play a crucial role in regulating the immune response. IL-1 is produced by various cells, including macrophages and monocytes, and it has multiple functions, including promoting inflammation and fever. Therefore, IL-1 is the correct answer as it is an interleukin and also known as IL-1.

The correct answer is "ALL OF THE ABOVE". In the DN3 phase or region 3 of T cell development, several characteristics occur. First, cells commit to the T cell lineage, meaning they differentiate into T cells. Second, TCR B-chain rearrangement occurs, which is an important step in T cell development. Third, T cell lineages alpha/beta or gamma/delta diverge, indicating the differentiation of T cells into different subsets. Finally, the cell surface markers CD44-CD25+CD4-CD8- are present during the DN3 phase. Therefore, all of these characteristics are observed in the DN3 phase or region 3 of T cell development.

TH17 plays a role in enhancing leukocyte recruitment and inflammation. It recognizes antigens of microbes ingested by macrophages and activates macrophages through the expression of CD40 ligand and secretion of IFN-gamma. This activation stimulates defense against intracellular microbes, leading to T cell and monocyte infiltration into tissues. The increased vascular permeability is caused by CD4+ T cells secreting cytokines, further enhancing the recruitment of leukocytes and promoting inflammation. This response is particularly important when macrophages are not activated by the microbes themselves or when pathogenic microbes have evolved to resist innate immune defenses.

The correct answer is IL-1, IL-6, IL-12, IL-18, IFN-A, IFN-B, and TNF-A. These cytokines are part of the innate immune response, which is the body's first line of defense against pathogens. IL-1 and IL-6 are involved in inflammation and fever response. IL-12 and IL-18 help activate natural killer cells and T cells. IFN-A and IFN-B are antiviral cytokines, and TNF-A is involved in inflammation and cell death. Together, these cytokines play crucial roles in initiating and coordinating the innate immune response to protect the body from infections.

CD28-B7 and CD40-CD40L interactions are essential for dialogue between B and T cells. CD28 is a receptor found on T cells, while B7 is a ligand found on antigen-presenting cells. This interaction provides a co-stimulatory signal necessary for T cell activation and proliferation. CD40 is a receptor found on B cells, while CD40L (also known as CD154) is a ligand found on activated T cells. This interaction is critical for B cell activation, differentiation, and antibody production. Both of these interactions play crucial roles in the immune response and coordination between B and T cells.

CD25+CD44+CD4-CD8- refers to a specific subset of immune cells called double negative T cells. These cells are typically found in Region 2 of the thymus. The thymus is an organ located in the chest, behind the breastbone, and is responsible for the development and maturation of T cells. Region 2 of the thymus is where these double negative T cells undergo further differentiation and selection processes before they mature into functional T cells. Therefore, it is in Region 2 of the thymus where one would expect to find CD25+CD44+CD4-CD8- cells.

The T cell's fate is determined at Stage 4.

The statement is false because cells entering the cortico-medullary junction do not express CD3 on their cell surface. CD3 is a protein complex that is primarily found on T cells, which are a type of white blood cell. The cortico-medullary junction is a region in the kidney where the cortex and medulla meet. While various cell types can be found in this region, CD3 expression is not a characteristic feature of these cells. Therefore, the correct answer is false.

The correct answer is ~ 10^15. This indicates that A/B TCRs have a total diversity of around 10^15. This means that there are approximately 10^15 different possible combinations of A/B TCRs, highlighting the high level of diversity within the A/B TCR repertoire. This diversity allows the immune system to recognize and respond to a wide range of antigens.

CD8+ T cells can activate macrophages when the macrophages express class I MHC molecules. This recognition triggers the activation of macrophages in the same way as CD4+ T cells, but it is not useful because macrophages cannot digest intracellular microbes. This suggests that CD8+ T cell response is not effective in activating macrophages to kill ingested microbes, unlike CD4+ T cell response which can activate macrophages to eliminate reservoires of infection.

IL-4 and IL-10 are the signature cytokines produced by TH2 cells. IL-4 is involved in promoting the differentiation of B cells into plasma cells and the production of IgE antibodies. It also plays a role in allergic responses and the recruitment of eosinophils. IL-10, on the other hand, is an anti-inflammatory cytokine that inhibits the production of pro-inflammatory cytokines and downregulates the immune response. Both IL-4 and IL-10 are important in regulating immune responses and maintaining immune homeostasis.

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The correct answer is "ALL OF THE ABOVE" because CD3 exists as only dimeric molecules. It can exist as homodimeric zeta-zeta or zeta-nu combinations, as well as heterodimeric non-covalently associated gamma and epsilon combination, and heterodimeric non-covalently associated epsilon and delta combination. Therefore, all of these options are correct.

Follicular dendritic cells hold intact, unprocessed long-lived immune complexes on their surface. This means that these cells can capture and retain large antigen-antibody complexes for an extended period of time. This function is important for the presentation of antigens to B cells, as it allows for the prolonged exposure of antigens to B cells in the germinal centers of lymphoid follicles. By holding onto these intact immune complexes, follicular dendritic cells contribute to the generation of an effective immune response.

E series prostaglandins, TGF-B, IL-4, and IL-10 are all molecules that can act as macrophage deactivating factors. These molecules can inhibit macrophage functions, including the release of TNF-A.