Acute phase reactions:

A. Fever:

• Most important systemic manifestation when inflammation is associated with infection.
• It is a syndrome in which there is alteration in metabolic activities, functional disturbances such as increased pulse rate, anorexia, nausea, vomiting, constipation, thirst, scanty urination and dehydration, besides abnormal rise in temperature.
• Causes includes: bacterial toxins, virus, fungi, protozoa, hypersensitivity reactions, severe traumatic injuries, surgical operations, vascular disturbances, neoplasms.

B. Other Acute Phase Reactions:

• Increased sleep
• Decreased appetite
• Increased degradation of skeletal muscle protein
• Hypotension
• Synthesis of acute phase protein by liver including C-reactive protein, serum amyloid A and serum amyloid P.

C. Change in Peripheral Blood Leukocytes:

• Leukocytosis is common feature of inflammatory reaction. It is due to increase in number of neutrophils.
• Normal leukocyte count:4000-10,000/µL

In case of inflammatory reactions: 15,000-20,000/µL.

But in some cases, they reach upto 40,000-1,00,000/µL. these extreme elevations of leukocytes are called leukaemoid reactions.

• Leukocytosis is due to accelerated release of white cells from bone marrow reserve pools.

Note:

• Left shift: Increase in number of immature neutrophils in blood.
• Right shift: ratio of immature to mature neutrophils with reduced count of young neutrophils (metamyelocytes).