Infection and immunity

Question 1

What is a fever?

Answer 1

Body temperature over 38 degree Celsius

Question 2

What does a fever indicate?

Answer 2

It indicates an elevated core body temperature in response to cytokines and acute phase proteins

Question 3

Name some accompanying symptoms of fever

Answer 3

• shivering
• night sweats
• severe headaches
• delirium
• muscle pain: common in viral infections
• shock: in severe infections and sepsis

Question 4

Fever is an indicator of underlying disease. TRUE OR FALSE

Answer 4

TRUE

Question 5

Name some investigations that should be carried out in patients with a fever

Answer 5

• FBC and eosinophil count
• urea and electrolytes
• liver function test
• inflammatory markers (esr and crp)
• ECG
• Throat swab
• Stool culture
• Urinalysis and urine culture

Question 6

Name 3 infections that present with a fever (differential diagnosis)

Answer 6

• Hepatitis
• Meningitis
• Pneumonia

Question 7

How do you manage a fever?

Answer 7

• simple analgesia e.g ibuprofen or paracetamol
• tepid sponging to cool the skin
• further management should be based on the underlying cause

Question 8

What is sepsis?

Answer 8

• extreme medical condition that arises as a result of body’s inflammatory response to infection

Question 9

Sepsis is one of the most common causes of multi-organ failure. TRUE OR FALSE

Answer 9

TRUE - sepsis causes severe inflammatory response in the entire body and immune system goes into overdrive

Question 10

What population is generally more likely to develop sepsis?

Answer 10

Elderly

Question 11

What are the kind of symptoms present in sepsis?

Answer 11

• Hypotension
• Altered mental status (Delusion etc.)
• Tachypnoea ( respiratory rate more than 22 b/m)
• suspected infection
• fever
• dizziness
• warm skin

Question 12

How do you investigate sepsis?

Answer 12

• Deliver high - flow oxygen
• Take blood cultures
• Administer IV antibiotics
• Measure serum lactate (corresponds to the level of oxygen starvation)
• Start IV fluids (increases blood pressure)
• Measure urine output
• Check vitals e.g bp, tpr etc.

Question 13

What is the prognosis of sepsis?

Answer 13

high mortality rate

- hospitalisation with sepsis can cause muscle wasting and damage inflicted organs

Question 14

What is the pathophysiology of sepsis

Answer 14

1. Infection
2. WBC release inflammatory cytokines
3. Blood vessels permeability increases so that wbc can infiltrate
4. Vasodilation throughout the body occurs
5. Blood pressure drops
6. Blood pressure also means less oxygen is supplied to cells and tissue
7. Immune response causes fluid build up that makes oxygen diffusion to cells and tissues more difficult
8. Leads to cell oxygen starvation

Question 15

List 3 microorganism which cause infections which commonly present to primary care

Answer 15

• C. diff
• E.coli
• Staphylococcus aureus

Question 16

Name some of the innate systems barriers against infection

Answer 16

1. Physical
   - Stomach acid
   - Ciliated epithelial cells
   - Mucus lining trachea
   - Skin surface (flora)
   - Co enzymes in tears
2. Internal defences
   - Inflammatory response
   - Complement system
   - Phagocytosis
   - Natural killer cells

Question 17

Common defects in innate immunity resulting in disease

Answer 17

1. Toll - like receptors deficiency: found on the surface of many wbc and react with proteins present on many microbes - activate secretion of cytokines for adaptive immunity
2. Natural Killer Cell deficiency: important in the killing of viral- infected of malignant cells (called NK cells because they do not need T- cells)
3. Defects in interferon - y and interleukin- 12 signalling: causes susceptibility to mycobacteria and salmonella infections

Question 18

How do NK cells kill viruses

Answer 18

They insert toxic proteins into their membranes and are particularly important in the defence against herpes virus

Question 19

How do PAMPS recognize MAMPS

Answer 19

They recognise that its not one of the self antigens so they bind to it

Question 20

ANTIBODIES MODE OF ACTION:

1. Prevents antigen from …..(2)…. to its target
2. Tagging a pathogen for destruction by ….(2) ……or neutrophils
3. Activating the ……(3)…… cascade
4. Opsonization
5. A…..(4)…….

Answer 20

1. binding
2. macrophages
3. complement
4. agglutination

Question 21

Describe the positive and negative selection of T and B cells

Answer 21

Positive selection requires signaling through the antigen receptor for the cell to survive. Developing B cells are positively selected when the pre-B receptor binds its ligand. (Developing T cells are positively selected for their ability to bind MHC as well as peptide.) Negative selection means that binding to the receptor results in cell death. Both immature B and T cells are negatively selected if they bind self antigen.

Question 22

What are effector cells?

Answer 22

Short lived cells that are activated and defend the immune system

Question 23

What is the role of effector cells in the cell mediated and humoral response?

Answer 23

Effector B cells are called plasma cells and secrete antibodies (humoral), and activated T cells include cytotoxic T cells and helper T cells, which carry out cell-mediated responses.

Question 24

What is sequestrum?

Answer 24

segment of necrotic bone that becomes separated or “sequestered” from the healthy intact bone.