Cells of chronic Inflammation:

1. Macrophages:

• main component of chronic inflammation.
• Monocytes emigrate into sites of inflammation and gets converted into large phagocytic cell which is known as macrophages.
• These belong to mononuclear phagocyte system (MPS).
• Highly specialized for phagocytic and intracellular digestion.
• Fc receptors which recognizes Fc fragment of IgG and complement receptors 1,2,3 which interact with complement fragment. C3b and C3bi, on surface of mast cell, mediates uptake of particles.
• These are “second line of cellular defence” as they completely destroy irritant through powerful enzymes and remove necrotic tissue from area.
  Due to their potential/capacity of getting activated, they can increase their size, increase level of lysosomal enzymes, increase ability to phagocytose and kill ingested bacteria.
• Activation signals: cytokines, mainly interferon-γ and Non-immunological stimuli
• after activation they secretes biologically active products which includes:

I. Enzymes:

• Natural proteases
• Elastase
• Collagenase
• Plasminogen activator:
• Acid hydrolases
• Phosphatases
• Lipases

II. Plasma proteins: Complement proteins, coagulation factors (V,VIII, tissue factor)
III. Reactive oxygen species
IV. Arachidonic acid metabolites: leukotrienes, prostaglandin
V. Cytokines: Chemokines (IL-1, TNF, IL-8)
VI. Growth factor
VII. Nitric oxide

2. Lymphocytes:

• Usually appear late and important cells in chronic inflammation.
• Comprise 40-60% of total blood leukocytes.
• Both T-lymphocytes and B-lymphocytes appear at sites of inflammation.
• Mobilized in both anti-body mediated and cell-mediated immune reactions as well as non-immune mediated inflammation.
• Activated lymphocytes produce cytokines which stimulates monocytes and macrophages. Activated macrophages then release cytokines including IL-1 and TNF that further activate lymphocytes.

3. Plasma cells:

• They are present in tissues.
• Contain more cytoplasm than lymphocytes and are larger.
• Characterized by eccentrically placed nucleus and spherical in shape.
• Donot undergo mitosis and originate from B-lymphocytes.
• Main function is to produce, store and secrete antibodies.

4. Giant cells:

• Macrophages fuses to form large phagocytic cell, which is called giant cell.
• These are of two types: Foreign body type and Tumor giant cells
• Foreign-body type are produced by fusion of macrophages in response to foreign material.
• They have multiple nuclei and nuclei are arranged around periphery of cell giving appearance of horse shoe.
• Langhan’s giant cells of tuberculosis are good examples of foreign-body giant cells.