Subcutaneous Injection of Bacterial Antigen to Induce Systemic Inflammation in a Murine Model

To induce systemic inflammation — a widespread inflammatory response, begin by positioning an anesthetized mouse with its dorsal side up. Take a syringe containing mycobacterial emulsion of mycobacterial antigen-adjuvant depots — a localized oil reservoir of the antigen-adjuvant mixture.

Pierce the mouse's epidermis and dermis skin layers and inject the antigen-adjuvant emulsion subcutaneously proximal to the inguinal lymph node. Post-injection, the depot continuously releases antigens into the surrounding tissue — providing prolonged exposure of the antigens to the immune system.

Antigen-presenting cells, or APCs, in the tissue, interact with injected mycobacterial antigens, internalize, and process them into peptides. These peptides are then presented on the surface of APCs using major histocompatibility complexes, triggering the release of pro-inflammatory cytokines and chemokines.

This process generates localized inflammation and triggers the opening of lymphatic vessels, enabling the entry of immune cells including antigen-carrying APCs into the lymphatic system and reaching the inguinal lymph node.

In lymph nodes, T cell receptors of helper T cells interact with antigens on the APCs' surface and become activated. The activated T cells release pro-inflammatory cytokines, which travel through lymphatic vessels and get released into various other tissues.

The released pro-inflammatory cytokines attract the immune cells to these tissues, inducing systemic inflammation.