Session 6: CRP

Question 1

What is CRP?

Answer 1

Acute phase protein, part of the acute phase reaction produced by the liver

Question 2

Why is the liver linked to an infection (or inflammation) elsewhere in the body?

Answer 2

Microorganisms in particular bacteria but also fungi have cell wall products e.g. lipopolysaccharies which activate macrophages and monocytes (innate immune response).

The macrophages and monocytes produce cytokinese - intercellular signaling polypeptide messengers such as Interleukin I, Interleukin 6 and Tumour Necrosis Factor which circulate in the blood

They (esp. Interleukin 6) stimulate hepatocytes to produce acute phase proteins

Question 3

What are acute phase proteins?

Answer 3

C-reactive protein, complement system, fibrinogen and many others.

The function of CRP is opsonin (see Innate Immunity Lecture Week 3)

Question 4

Why is CRP useful?

Answer 4

• Up to 1000 fold increase (produced in large amounts)
• Rapid production (within hours)
• Easy to measure
• CRP is raised in

Infection

Trauma

Surgery

Burns

Tissue infarction

Inflammation

Cancer

Question 5

What is the erythrocyte sedimentation rate?

Answer 5

• The rate at which red cells sediment in one hour
• In inflammation: increased fibrinogen (acute phase protein) causes red cells to stick together and these settle faster
• ESR is increased

Question 6

What are other acute-phase phenomena?

Answer 6

Fever (hypothalamus is triggered by cytokines)

Hormone secretion (e.g. cortisol)

Blood changes (anaemia of chronic disease)

Metabolic changes

Question 7

What is a Gram Stain? How is it performed?

Answer 7

Gram Staining divides most bacteria into two groups. Gram staining depends on the ability of certain bacteria (the Gram-Positives) to retain a complex of purple dye and iodine when challenged with a brief alcohol wash. Gram negatives do not retain the dye. This distinction turns out to be correlated with fundamental differences in the cell envelopes of the two classes of bacteria.

1. Stain with crystal violet (purple)
2. Modify with potassium iodide
3. Decolorize with alcohol; only gram-positives remain purple
4. Counterstain with safranin: Gram-negatives become pink; Gram-positives remain purple

Question 8

What are the differences in the cell envelopes between Gram Positive and Gram Negative bacteria?

Answer 8

• Gram positive has a much thicker peptidoglycan layer in the cell envelope (20x increase)
• Gram negative has a covering of lipopolysaccharides. The Gram-negative’s outer membrane also has pores made of trimers of porin, which permit the entry of small hydrophilic molecules.