Lymphocytes Flashcards

Question

What makes up the epitope recognized by T cell receptors?

Answer 1

Combination of part of antigenic protein and MHCII

Answer 2

T cells detect the presence of an intracellular pathogen because the infected cells/professional APC antigen presenting cells display peptide fragments of the pathogen’s proteins on their surface. These foreign peptides are delivered to the cell surface by specialized host-cell glycoproteins - the Major Histocompatibility Complex (MHC) molecules.

Answer 3

- major role in defining self and non-self antigens - Presents antigens to T cells - Critical in surgery and donor matching

Answer 4

MHC1 - All nucleated cells, screening mechanism | MHC2 - Professional antigen presenting cell

Answer 5

MHCI glycoproteins detect foreign peptides and tell dendritic cells which express more MHCII - professional APCs T cells then detect the presence of an intracellular pathogen because the infected cells/professional APC display peptide fragments of the pathogen’s proteins on their surface

Answer 6

MHCI binds to CD8 T-cells and are present on all nucleated cells MHCII bind to CD4 T-cells and are only found on professional antigen presenting cells - dendritic cells, B lymphocytes and macrophages

Answer 7

MHCI presented by the target cell (Intracellular pathogen or antigen) and is presented to CD8 cells MHCII presented by the antigen presenting cell to the CD4 cells

Answer 8

Nearly all somatic cells (except red blood cells) express MHC class I molecules. CD8 cytotoxic T cell is primarily responsible for pathogen surveillance and cytolysis of somatic cells. Antigens derived from viruses/bacteria multiplying inside the cytosol of an infected cell are displayed on the cell’s surface by MHC I, where they are recognized by the antigen receptors of cytotoxic T cells. The CD8 cell scans cells, looking for MHC showing non-self; normally, in uninfected cells, MHC I molecules show self peptides.

Answer 9

CD4 T cells recognise antigen presented by MHC class II proteins, which are expressed by the predominant antigen-presenting cells of the immune system: dendritic cells, macrophages, and B cells. Thus CD4 T cells tend to recognize antigens taken up by phagocytosis from the extracellular environment (exogenous antigens) CD4 T cells differentiate into several subsets of effector T cells that orchestrate different immune functions.

Answer 10

Co-dominant (maternla and paternal genes are both expressed) therefore each person can have up to 6 of each gene if completely heterozygous More than 17,000 MHC variants

Answer 11

Co-dominant (maternla and paternal genes are both expressed) therefore each person can have up to 6 of each gene if completely heterozygous More than 17,000 MHC variants

Answer 12

MHC is polygenic = it contains several different MHC class I and MHC class II genes, so that every individual possesses a set of MHC molecules with different ranges of peptide-binding specificities. MHC is highly polymorphic = that is, there are multiple variants, or alleles, of each gene within the population as a whole.

Answer 13

BCR - surface bound antibody | This encodes the antibody that the b-cell will make

Answer 14

Neutralisation Opsonisation Complement activation

Answer 15

Antigen - thymus independent | T cells - thymus dependent

Answer 16

The membrane bound BCR recognises (thymus-dependent) antigen The receptor-bound antigen is internalised and degraded into peptides Peptides associate with “self” molecules (MHC class II) and is expressed at the cell surface This complex is recognised by matched CD4 T helper cell B cell activated - T cell will secrete cytokines which may switch the BCR AB class (in proliferating activated B cells) depending on the response needed.(class switched, mature plasma/memory cell)

Answer 17

Some microbial constituents can induce antibody production in the absence of helper T cells These microbial antigens are known as thymus-independent antigens Such antigens are typically highly repetitive molecules, such as the polysaccharides of bacterial cell walls, and can cross-link the BCR on B cells. A second signal triggered from direct recognition of a common microbial constituent such as LPS (activating TLR signalling in the B cell) Only IgM; no memory

Answer 18

Clonal selection - selection of specific B-cell which will produce the correct antibody Clonal expansion - foreign antigen interacts with the receptor on a B-cell, activated and starts to divide. It gives rise to a clone of identical progeny, all of whose receptors bind the same antigen

Answer 19

``` IgG IgM IgA IgD IgE ```

Answer 20

Best kind of antibody highest opsonisation and neutralisation activities Four subclasses 1-4

Answer 21

First produced, upon antigen invasion | Not as specific and low affinity

Answer 22

A- Expressed in mucosal tissues | D- unknown function

Answer 23

Derived from stem cells in bone marrow - generation and maturation occurs in the bone marrow in the absence of antigen Migrate into the circulation and into lymphoid tissues

Answer 24

Consists of two heavy chains and two light chains The two heavy chains are linked to each other by disulfide bonds, and each heavy chain is linked to a light chain by a disulfide bond. Two identical antigen-binding sites (bind simultaneously to two identical antigens on a surface) Two types of light chains, lambda (λ) and kappa (κ), are found in antibodies (never one of each in an antibody)

Answer 25

antibodies coat a bacterial cell; C regions form a platform that more efficiently activate complement proteins (covalent deposition on bacterial surface) => complement proteins on the bacterium can be recognized by complement receptors on phagocytes; this stimulates the phagocytes to ingest and destroy the bacterium.

Answer 26

antibodies coat bacterium to better enable a phagocytic cell such as a macrophage or a neutrophil to ingest and destroy it (Fc receptors on phagocytic cell binds to C region)

Answer 27

antibodies bind to viruses/bacterial toxins and thereby block their access to cells that they might infect or destroy