6.7 Response to infection

What is a pathogen?

Organisms cause harm by invading and destroying host tissues and producing toxins

What are examples of pathogens?

• Lamda phage

• RNA viruses

• TMV

• Ebola

• Staphylococcus Aureus

• Stem rust fungus

• Myobacterium

• Influenza

• Plasmodium

What are some barriers to non-specific infection?

• Skin

• Blood clotting

• Stomach acid

• Mucus and cilia

• Antibacterial chemicals in sweat and tears

Skin

Physical and waterproof (keratin)

Blood clotting

Quick seal any breaks in skin

Stomach acid

Destroys ingested pathogens

Mucus and cilia

Trap + remove pathogens

Cilia waft mucus to stomach

Antibacterial chems

Lysozymes (digestive enzymes) found in sweat and tears

Kill bacteria

What are eosinophils

Parasitic function

Regulate allergic responses

What are monocytes?

Type of phagocytic cell

Macrophages

• Phagocytic cells

• Kidney chased nucleus

• Mature from monocytes

• Produced in bone marrow

Macrophage function

Engulf foreign cells, particles and infectious agents

Process them + present to lymphocytes

What cells are found in bone marrow?

WBCs and RBCs

Neutrophils

• Phagocytic

• lobed nucleus

• Short live, large quant in bone marrow

• Found in all tissues at site of injury

Neutrophil function

Engulf and destroy foreign cells, particles and infectious agents by phagocytosis

Lymphocytes

• Non phagocytic cells

What do lymphocytes do?

Mature in bone marrow B for bone

or migrate to and mature in thymus gland T for thymus gland

Lymphocytes function

• Differentiate into many different types of cells

Lymphocytes functions

• Killing infected cells

• Producing antibodies = providing immunity

Outline non-specific immune response

• Offers protection against all pathogens encountered without any specificity

• Lacks immunological mem, so rs are at same each time patho is encountered

• Quicker than specific I r

What components of non-s defences are always present?

Barriers to infection - phagocytic less

How is non specific i r activated?

Histamine, complement and interferons

Where is histamine found?

Amine stored in granules of basophils

What happens when histamine is released from its granules?

Histamine = arterioles dilate + increase in permeability of capillaries

= plasma, leukocytes + blood plasma, proteins leak from bloodstream

Where do they leak from the bloodstream to?

Vessel walls + migrate to site of tissue injury of infection

Fight infection and help heal injured tissue

What is apoptosis?

Cell death

Complement

Complex system of more than 30 proteins

Eliminate infectious microorganisms

Where are the complement proteins produced?

Liver

What activates the complement?

Histamine

What happens to complement once activated?

Proteins = lysis of foreign and infected cells

Phagocytes of foreign particles, cell debris + inflammatory of surround tiss

What are interferons?

• Group of proteins released by nucleus in response to presence of viruses

What do interferons do?

Virus infected cell will release interferons

= nearby cells heighten anti-viral defences

Are interferons cytokine?

Yes, used for communication bet cells to = protective defences of immune s

What is cytokine?

Cell signalling molecule

What do interferons do?

Infected cells = apoptosis = make infected cells = more obvs to killer cells = production of anti-viral enzymes in nearby cells

What are the anti-viral enzymes called?

Ribonuclease

Protein kinase

What are pseudopodia?

Fake feet

What type of reaction is digestion?

Hydrolysis as it requires water

Process of phagocytosis

1. Phagocyte extends its cell surf mem (forming pseudopodia) + pathogen

2. Cell surf mem meets + fuses = phagocytic vesicle

3. Lysosomes (containing lysozyme) move to + fuse w phagocytic vesicles

4. Hydrolytic enzymes from lysosomes digest pathogens

5. Products of digestion absorbed by cell

6. Undigested material is released by exocytosis

What can be antigens?

Glycoprotein, glycolipid and protein

What are antigens

Mols, usually on surface of a cell = immune r

How does a cell surface identify antigens?

Each cell has specific antigens on its surface

What do antigens enable immune s to do?

identify

• pathogens

• Cells from other organisms of same species

• Abnormal body cells (infected or cancerous cells)

What is antigen variability?

Change antigens through mutation

= immunity + disease protection diffi

Would an MHC be similiar to family members

Yes

What does MHC stand for

Major histocompatibility complex

What is MHC

Collection of glycoproteins on surf of cell that identifies it as self

Why is MHC unique to individual

Gen determined and inherited f

Where are genes for MHC found

Found on chromosome 6

What is role of MHC?

• prevents immune s attacking its own cells

• Used in antigen presentation

What do lymphocytes have antigen receptors that can…

• recognise MHC antigens

• Differentiate bet these + foreign antigens

(A) (I) For antibody A, compare increase in mean level after vaccination with mean level after infection of Bortella pertussis

B) (I) Explain the changes in mean level of antibody A after infection with Bordtella pertussis

B (ii) Suggest why antibody B was not present in blood of these rats until after infection with Bordetella pertussis

C) Comment on reliability

(A) Levels of antibody rise sooner higher and faster after infection

(A) (I) sec I. R memory cells, 2nd exposure mem cells stimulated, sec r antibodies produced from plasma cells

B I) antibodies present if antigen is present antigen is not present in vaccine

C) no error bars, no control variables, stats analysis