key aspects of the immune response

Question 1

what are the classes of adaptive immune response

Answer 1

1. antibody response (humoral) - antibodies produced by B lymphocytes (B cells/ plasma cells)
2. Cell mediated response- involves T lymphocytes- recognise cell associated antigens.3 basic types helper Tcells,Cytotoxic T cells, regulatory T cells. T cells need antigens presented to them by antigen presenting cells e.g. macrophages, neutrophils, B cells

Question 2

cytotoxic T (Tc) cell activation

Answer 2

1 stimulator cell expressing class 1 MHC presents antigen to a pre-cytotoxic T cell
2. antigen presenting cell presents antigen in association with class 2 MHC to CD4+ T cell
3. CD4+ T cell makes cytokines (e.g. IL-2, IFN)
IL-2 causes Tc-cells to mature and divide
4. Pre CTL differentiates to functional CTL
5.CD8 CTL recognises class 1 MHC-expressing target cell that displays antigen
6.target cell is lyzed

Question 3

can cytotoxic T cells have immunological memory

Answer 3

Tc- cells may be activated by IL-2 from T-helper cells

some will become cytotoxic T-cells that kill abnormal and infected cells and others will become memory cytotoxic T cells

Question 4

where do the Mature B cells develop

Answer 4

Mature B cells develop from a lymphoid progenitor cell in the bone marrow

Question 5

where do the Mature T cells develop

Answer 5

Mature T cells develop from a lymphoid progenitor cell in thymus

Question 6

where do the innate immune cells develop

Answer 6

Innate immune cells develop from myeloid progenitor cell, again in the bone marrow

Question 7

antigen (Ag)

Answer 7

mostly multiple specific sites of interaction on an antigen with a specific antibody : therefore multiple antibodies can bind to an antigen. The antigen binding site on an antibody is a paratope. they are multivalent. they all possess antigenicity which is the ability of a molecule to specifically interact with a B-cell receptor or T -cell receptor

Question 8

types of antigens

Answer 8

proteins- most common
polysaccharide
lipids/glycolipids
nucleic acids

Question 9

epitope

Answer 9

epitope(antigenic determinant) is the part of the antigen that interacts with the antibody.
most antigens contain several epitopes and the number of epitopes is > or = to the valence of the antigen.

Question 10

antigen valence

Answer 10

indicates how many different antibodies are bound by an antigen. Antigen valence is smaller or equal to the number of epitopes. This is due to the shape if antibodies blocking access to some epitopes

Question 11

protein epitope types

Answer 11

linear epitope
conformational epitope
buried epitope: hidden or new

Question 12

linear epitopes

Answer 12

are sequential epitopes
are present in the primary structure of protein. no changes of structure required as the antibodies can bind to the primary sequence

Question 13

conformational epitope

Answer 13

non sequential epitope
tertiary protein structure recognised
is discontinuous
(see lecture image if confused)

Question 14

buried epitope

Answer 14

linear epitope is buried within a protein due to its folding. its only when the protein is unfolded that the epitope is revealed. E.g human papilloma virus (HPV). another example is a peanut allergy- digestion exposes this buried epitope

Question 15

immunogen

Answer 15

antigen that can induce an immune response
interacts with B-cells and or T-cells (antigenicity) and in addition causes an immune response (immunogenicity)
only proteins are fully immunogenic: induce T-cells

Question 16

types of immunogens

Answer 16

• soluble substances - toxins (e.g. cholera, diphtheria),proteins
• viral substance
• molecules on particulate samples: pathogenic and non-pathogenic organisms, tissue cells

Question 17

effect of immunogen exposure

Answer 17

antibody production
one B cell clone produces a highly specific antibody to one epitope of an antigen
=receptor-specificity is true for B and T cells
Plasma cells produce secreted antibodies
Therefore complex immunogens with several epitopes will cause production of different epitope-specific antibodies all reacting with the same antigen. This is the basis of polyclonal antibodies

Question 18

factors effecting immunogenicity of antigens

Answer 18

• immunogen contribution-the property’s of the imunogen
• biological system contribution-propertys of the host(genetic variation)
• administration of immunogen

Question 19

Hapten

Answer 19

small substances that contain a single epitope
free haptens can interact with products of immune response once these have been elicited
free haptens cannot induce immune response
- they posses property of antigenicity but not immunogenicity