W11 Intro to immune system

Question 1

Immunology

Answer 1

is the study of our body’s systems for preventing disease

Question 2

Organisation of the Immune System

Answer 2

Innate Immunity – front line defence

then

Adaptive immunity – specific and memory responses

then

Humoral – B cells and antibodies

Humoral – B cells and antibodies

Question 3

The innate immune system

Answer 3

is your ever-present defense against infection. It is made up of barriers that keep viruses, bacteria, parasites, and other foreign particles out of your body or limit their ability to spread and move throughout the body

Question 4

The importance of innate immunity

Answer 4

is demonstrated by the fact that you are normally healthy despite the barrage of potential infectious challenges you face every minute.

Question 5

The innate immune system includes:

Answer 5

Epithelial barriers to the environment (eg skin, gastro-intestinal tract, respiratory tract) that prevent microbe entry.

Secretions at mucosal surfaces – flushing action and antimicrobial properties.

Cells that are resident in tissues (eg mast cells) or circulating in the body (eg neutrophils).

Circulating proteins in the blood (eg complement proteins).

Cytokines (eg interferons) that are locally produced by infected cells.

Non-specific activity.
No “memory”, the response is the same to repeated challenge.

Question 6

PAMPs

Answer 6

are small molecular motifs conserved within a class of microbes. A vast array include glycans, lipopolysaccharides, bacterial flagellin, lipoteichoic acid, peptidoglycan and nucleic acid variants normally associated with viruses, such as double-stranded RNA

Question 7

DAMPs

Answer 7

are molecules released by stressed cells undergoing necrosis. Some are proteins - heat-shock proteins and cytokines. Non-protein DAMPs include ATP, heparin sulfate, and DNA

Question 8

PAMPS and DAMPS are recognized by

Answer 8

by Pattern Recognition Receptors (PRRs) on immune cells

Question 9

Phagocytosis

Answer 9

is a processby which cells internalise solid matter, including microbial pathogens

a mechanism by which microorganisms can be contained, killed and processed for antigen presentation

Question 10

Inflammation

Answer 10

is the process whereby immune cells (which are normally distributed throughout the body) can be recruited and concentrated to a site of infection or damage

Question 11

Following PAMP or DAMP recognition

Answer 11

PRRs trigger proinflammatory and antimicrobial responses by inducing the release of a broad range of cytokines

Question 12

The main events in inflammation are:

Answer 12

Increased blood supply to the affected area;
Increased permeability of the vasculature ;
Migration of WBCs out of the blood capillaries into the affected tissue

Question 13

Dendritic cells

Answer 13

capture, process and present antigens

Question 14

T lymphocytes

Answer 14

control the immune response by providing “help” to B cells and macrophages (helper T cells); direct killing of infected or tumour cells (cytotoxic T cells).

1-4x10^9/l in blood

Question 15

Cytokines

Answer 15

soluble proteins secreted mainly by T cells that control activities of other cells

Question 16

B lymphocytes

Answer 16

produce and secrete antibodies, proteins that specifically bind target molecules (antigens) on microbes or cells

1-4x10^9/l in blood

Question 17

The Lymphoid System

Answer 17

Immunological cells are largely organised into tissues and organs for best efficiency.
Collectively, these structures are known as the lymphoid system.

Question 18

Primary lymphoid organs

Answer 18

are the sites of maturation of white blood cells – they differentiate from stem cells, multiply, are programmed and mature into functional cells.

Question 19

Secondary lymphoid organs

Answer 19

provide the site for interaction between antigens and WBCs. They also allow spread of the immune response.
Secondary lymphoid organs are associated with systemic and mucosal immune compartments (blue).

Question 20

TheLymphatic System

Answer 20

The lymphatic system is part of thecirculatory systemand an important part of theimmune system. It comprises a network oflymphatic vesselsthat carry lymph fluid and cells from the tissues back into the blood stream

Question 21

Lymph Nodes

Answer 21

At regular intervals along the lymph vessels are organised structures – lymph nodes

Question 22

Lymp entrance/exit

Answer 22

Lymph arrives at the node by an afferent lymphatic vessel, it filters through multiple layers of antigen presenting cells, T cells and B cells, and exits via the efferent lymphatic vessel

Question 23

dense concentration of immune cells provides..

Answer 23

an ideal environment for initiating immune responses and communication between immune cells. Lymph nodes are common battleground sites for the immune system and infections.

Question 24

Immunoglobulins (Igs)

Answer 24

Immunoglobulins (antibodies), are glycoproteins produced by plasma cells.

They specifically recognise and bind strongly to particular antigens on pathogens, and prevent disease or aid in the destruction of the pathogen.

There are different classes and subclasses of immunoglobulins, which differ in their structure, biological features and distribution.

Immunoglobulins are produced by B cells – humoral immunity

Question 25

T-cell antigen receptors (TCRs)

Answer 25

T-cell receptors are found on the surface ofT cells. They are responsible for recognizing processed fragments ofantigen (peptides)which are “presented” by host cells.

The binding between TCR and antigen peptides is relatively weak compared to antibodies.

When the TCR engages with antigenic peptide, the T lymphocyte is activated through a series of biochemical events (signal transduction), leading to cell proliferation and biological activity (eg cytokine production).

TCRs are produced by T cells – cellular immunity

Question 26

B cells

Answer 26

B cells are lymphocytes, which when activated, become plasma cells and then produce antibodies. This is often known as humoral immunity.

Question 27

Antibodies

Answer 27

Antibodies are glycoproteins that are made by B cells and plasma cells.

They bind specifically and with high affinity to “non-self” antigens.

Antigens are usually proteins or carbohydrates attached to, or secreted by, microbes and infected cells.

Antibodies can neutralise targets, or recruit other components of the immune system to kill targets

Question 28

Potential antibody repertoire

Answer 28

~10^15

Question 29

T cells – cell mediated (cellular) immunity

Answer 29

T cells control the immune response and combat microbes that are inside cells (intracellular)

Different T cells have different functions and are distinguished by the array of proteins on the cell surface (Cluster of Differentiation – CD – markers).

Two major groups are CD4 (helper T cells), and CD8 (cytotoxic T cells)

Question 30

foreign antigen fragments (peptides) are displayed at …

Answer 30

displayed at the cell surface by molecules of the major histocompatibility complex (MHC)

Question 31

T cells recognise antigens via

Answer 31

via cell-surface receptors (TCRs) proteins, that are related to antibodies.
But unlike antibodies, T cells do not recognise foreign molecules in their “native” state

Question 32

Mature cytotoxic T cells kill by

Answer 32

Mature cytotoxic T cells kill target cells using cytokines, cytotoxic granules and the caspase cascade.

Question 33

Mature helper T cells secrete…

Answer 33

Mature helper T cells secrete cytokines to “help” (activate) macrophages, B cells and other T cells

Question 34

Immunological techniques in diagnostics and research

Answer 34

Two key features of antibodies – antigen specificity and high affinity binding are extremely valuable in laboratory assays.
They allow rapid and highly sensitive identification of specific molecules.

Question 35

Immunological techniques in diagnostics and research

- examples

Answer 35

ELISA

Western blotting

Lateral flow assay

Fluorescence-activated cells sorting (FACS)