Immunology 1 - intro to immunology

Question 1

4 differences between the inate and adaptive immune response

Answer 1

innate - rpaid, already from birth, not as specific, no memory - same response with re exposure, ddetects alterations in haemostasis

Question 2

which innate immune cells get altered in the presence of bacteria?

Answer 2

Neutrophils and macrophages. Natural killer cells, dendritic cells, mast cells

Question 3

innate immune cells

Answer 3

neutrophils, basophils, eosinophil, monocyte (macrophage, denritic cells)

Question 4

which are in the blood?

Answer 4

baso, neutro, eosino, monocyte

Question 5

which are in the tissues

Answer 5

macrophage, dendritic cells, mast cells

Question 6

how are antigens detected?

Answer 6

cell sufrace receptors

Question 7

Which substances are released from these cells once they recognise the invasion?

Answer 7

cytokines

Question 8

what effect do cytokines have in helping the immune response?

Answer 8

vasodulation, increased vascular permiability, recruiting other immune cells

Question 9

By which ‘killing mechanism’ do these cells try to eradicate an invader?

Answer 9

phagocytosis

Question 10

other funcitons of the innate immune system

Answer 10

antigen presentation, inflammation, recruit cells, opsonisation, lysis

Question 11

define a antigen and antibody?

Answer 11

ag - A molecule capable of inducing an immune response

ab - A glycoprotein produced by B lymphocytes that binds antigens with a high degree of specificity and affinity

Question 12

what does MH1 and MH2 bind?

Answer 12

1 to 8, 2 to 4 (CD4/CD8)

Question 13

what happens once t cells differentiate?

Answer 13

T cells differentiate into naïve T cells within the thymus. These naïve T cells (either CD4+ or CD8+) then move to the lymph nodes where they encounter antigen presented by dendritic cells. At that point, if they recognise an antigen, they will proliferate into T helper cells (if CD4+) or cytotoxic T cells (if CD8+)

Question 14

how to dendritic cells work?

Answer 14

Present antigen via MHC2, Sentinel for the immune system. Excellent at activating adaptive immune system. Internalizes pathogen and processes it into peptides which it presents (antigen). T cells which have not seen antigen before (naïve) are activated

Question 15

name the adaptive immune cells

Answer 15

small lymphocyte –> T or B –> B matures to plasma cells

Question 16

where do t cells mature?

Answer 16

bone marrow and then thymus

Question 17

where do b cells mature?

Answer 17

bone marrow and then thymus. B and T cells then migrate to secondary lymphoid organs, where they encounter antigen

Question 18

what do CD4+ T cells differentiate into?

Answer 18

differentiate into distinct subsets of effector cells in response to antigen, co-stimulators, and cytokines. TH1, TH2, TH17

Question 19

function of THELPER1 cells

Answer 19

secretes IFNgamma, macrophage activation, igG production, host defence - intracellular microbes, role - autoimmune diseases, tissue damage, chronic infecrtions

Question 20

what are cytokines?

Answer 20

Large and heterogeneous soluble proteins
Communication system – act locally or at a distance
Regulate and co-ordinate the cells of innate and adaptive immunity ie regulate immune responses
Produced during normal haematopoiesis
Produced in response to microbes, tissue damage or other antigens
Produced by many cell types – esp macrophages and T helper cells

Question 21

what else can TH cells do in regard to B cells?

Answer 21

Some Th cells will help the B cell response so that B cells produce the correct antibody isotype and the antibody affinity improves

Question 22

how do CD8+ (cytotoxic) cells kill?

Answer 22

By inducing apoptosis in a targeted cell

Question 23

NK cells…

Answer 23

NK cells (innate system) are important against intracellular pathogens
NK cells may respond via their activating receptors to activating ligands on infected cells in TB or to antibody-tagged cells or directly to bacteria via TLR2
They can kill infected cells
They produce IFN-g which will help to stimulate macrophages, TH1 cells and CD8+ cytotoxic T cells
They are especially important if T cell response is not optimal

Question 24

outline the different immunoglobulin isotypes?

Answer 24

igM - best activating complement, igG - can cross the placenta, igA (dimer) - contained in secretions, igE - parasitic infections and allergy, igD

Question 25

how do B cells modulate immune responses?

Answer 25

Production of M. tuberculosis-specific antibodies can mediate the formation of immune complex that can modulate the functions of effector cells such as dendritic cells and macrophages. It remains to be demonstrated whether specific neutralizing antibodies exist. B cells can serve as antigen presenting cells to influence T cell activation, polarization, and effector functions and the establishment of T cell memory. B cells can also modulate the functions of granulomatous immune cells. In concert, these antibody-dependent and independent functions of B cells play an important role in determining disease outcome in terms of the elimination of control of bacteria, as well as the development of immunopathology that could damage tissues and promote dissemination

Question 26

what are the effector functions of antibodies?

Answer 26

Antibodies are produced by the activation of B lymphocytes by antigens and other signals (not shown). Antibodies of different heavy chain classes (isotypes) perform different effector functions.
Complement is an enzyme cascade system which can be activated to help the immune response - leading to inflammation.,
Opsonization is the tagging of a microbe so that it is phagocytosed more easily and efficiently. Antibodies and complement fragments can be opsonins.
Neutralization on microbes and toxins
Lysis of microbes
phagocytosis of microbes opsonized with complement fragments.

Question 27

OUTLINE ANTIBODY MEDIATED IMMUNITY

Answer 27

When a foreign antigen is first encountered, a lag phase occurs while activated B cells are differentiating into plasma cells. During the lag phase, no antibodies are produced. Once plasma cells have formed, a low volume of IgM antibodies are released to neutralise this initial infection, although small amounts of IgG can also be produced. Memory B cells that recognise the specific antigen are also produced.

If the same antigen is encountered again, there is an accelerated response initiated by these memory B cells which immediately recognise this antigen. Once activated, memory B cells quickly proliferate and create plasma cells, causing the fast release of a high volume of IgG antibodies specific to this antigen, as well as a low amount of IgM.
After the primary infection by a pathogen, a small pool of long-lived memory B and T cells specific to the pathogen’s antigen remain quiescent within the body. Memory cells can lie dormant for many years but are poised to respond rapidly if reinfection occurs. This is referred to as immunological memory.

Memory B cells are vital for generating an accelerated and more potent antibody-mediated immune response in secondary immune responses.

Memory T cells can either express CD4 or CD8, and respond rapidly if the host is re-exposed to a previously encountered antigen.