Inflammation is the body's response to various danger signals such as external pathogens, physical and chemical stimulation, and trauma. It plays a positive role in wound healing, tissue repair, maintaining tissue homeostasis, and preventing tissue function loss. This process involves the activation of innate and adaptive immune cells. When the physical barriers inside and outside the body cannot resist injury stimuli or pathogen invasion, the innate immune system is first activated, that is, macrophages respond to the injury and release cytokines and chemokines to recruit other innate immune cells such as neutrophils and dendritic cells, etc., accumulate at the site of injury. Macrophages and neutrophils phagocytose pathogens, and dendritic cells, as important antigen-presenting cells, can activate CD4+Th cells and CD8+T cells in lymph nodes to jointly eliminate pathogens with the adaptive immune system and promote tissue cells proliferation and repair, maintaining tissue homeostasis.

After the body is stimulated by inflammation, the monocyte/macrophage system is activated and affects the body's acute phase reactants (APR) by releasing a large number of cytokines (such as IL-6, IL-1β, TNF-α, IFN-γ, etc.) (mainly in the liver), thus changing its concentration in plasma. "Normal phase APR" mainly includes C-reactive protein (CRP), fibrinogen, ferritin (SF), complement, procalcitonin (PCT), serum amyloid (SAA), and haptoglobin. "Negative phase APR" mainly includes prealbumin, albumin and transferrin.

When inflammation occurs, the expression of positive-phase APR in plasma increases, and the production of negative-phase APR decreases. The concentration changes of APR, especially acute phase protein (APP), can not only reflect the progression of inflammatory diseases, but also have great significance in the clinical diagnosis and differential diagnosis of diseases.

Increased white blood cell/neutrophil and platelet counts are systemic responses when inflammation strikes, and ESR is accelerated by the increase in fibrinogen. These traditional inflammatory markers can be used as auxiliary reference indicators for the diagnosis of inflammatory diseases. Although these inflammatory indicators are easy to obtain, their specificity is poor and they are easily affected by factors such as age, gender, and anemia. They can also change under non-inflammatory conditions such as strenuous exercise, poisoning, and acute massive blood loss. Currently, commonly used clinical inflammatory markers include C-reactive protein (CRP), procalcitonin (PCT), serum amyloid A (SAA), and interleukin 6(IL-6) and heparin-binding protein (HBP), etc.