Innate immune and antigen-presenting cells at the injection site

Innate immune and antigen-presenting cells at the injection site represent the primary cellular interface between a vaccine or injectable therapeutic and the host's immune system. This population includes neutrophils, monocytes, macrophages, and dendritic cells that are recruited to or reside at the site of administration (Koff et al., 2013, Science). Upon injection, these cells recognize pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) via receptors such as Toll-like receptors (TLRs). This recognition triggers an inflammatory cascade that enhances the recruitment of professional antigen-presenting cells (APCs), which internalize the administered antigen and transport it to local lymph nodes (Pulendran & Ahmed, 2011, Nature). The activation of these cells is a critical step in the 'adjuvant effect,' which determines the strength, quality, and duration of the resulting adaptive immune response. While essential for vaccine efficacy, over-activation of these cells can lead to adverse local or systemic inflammatory events.

Other names

Injection site immune cellsLocal innate immune environmentVaccine-responsive antigen-presenting cellsInjection site APCs

Adjuvants and vaccines interact with these cells to trigger pattern recognition receptors (PRRs), leading to the recruitment of additional immune cells, antigen uptake, and subsequent migration to draining lymph nodes to prime T and B cell responses (Awate et al., 2013, Frontiers in Immunology).