Question

- How does acute inflammation lead to chronic inflammation?

- How is inflammation linked with aging?

Answer 1

-- Sometimes acute inflammatory response involving the neutrophils, eosinophils and mast cells fail to eleminate the pathogen either due to defect in the immune system or because of the resistance acquired by the microbes. Re-exposure to the antigen elecits a cell mediated immune response called Delayed -type Hypersensitivity. In this, instead of neutrophils, macrophages and T-lymphocytes increase in number. The T_H1  cells are activated which release cytokines. The cytokines cause macrophages to accumilate at the site of infection. Macrophages release lytic enzymes which cause injury to tissues which leads to tissue fibrosis. This results in long lasting damage to the tissues i.e chronic inflammation

-- Inflammatory reactions of the body may be impaired due to aging. Cellular debris, uric acid crystals and different metabolites accumulate either because of their increased production or delayed elemination. These substances send a danger signal as they mimic bacterial products and thus initiate an innate immune response.

Sometimes microbes inhabiting the mouth or gut and their products also diffuse to surrounding tissues as the ability of the body to process and eleminate them decreases with age. this also can stimulate low- grade immune response in the body.

Our immune system is very specific also. With aging they loose their specificity. They produce chemicals which not only damage the target cell, but damage their own body cells.

A lifetime exposure to pathogens and decades of molecular damage results into an overactive immune system which the aging body fails to turn off. A chronic inflammation starts. Many of the autoimmune disorders like Type 1 diabetes where the immune system of the body attack their own body cells is the result of aging.