Phagocytosis and antigen presentation in dendritic cells

Abstract

Like macrophages and neutrophils, dendritic cells (DCs) are considered professional phagocytes. Even if the three cell types phagocytose parasites, bacteria, cell debris, or even intact cells very efficiently, the functional outcomes of the phagocytic event are quite different. Macrophages and neutrophils scavenge and destroy phagocytosed particles, a critical step in innate immunity. DCs, in contrast, have developed means to 'preserve' useful information from the ingested particles that serve to initiate adaptive immune responses. Thus, both phagosomal degradation and acidification are much lower in DCs than in macrophages or neutrophils. Reduced degradation results in the conservation of antigenic peptides and in their increased presentation on major histocompatibility complex class I and II molecules. In this article, we review the mechanisms that control this delicate equilibrium between phagosomal degradation/cytotoxicity and antigen presentation in the different families of phagocytes.

Difference in TB10.4 T‐cell epitope recognition following immunization with recombinant TB10.4, BCG or infection with Mycobacterium tuberculosis

“…Thus, we next studied whether TB10.4 and BCG vaccines differed with regard to cellular uptake at the local draining LN (dLN), as it could be speculated that uptake into different cell types could lead to different Ag processing/epitope recognition patterns which could explain some of our observations [9].…”

“…Different APC have been shown to vary with regard to Ag processing pathways as well as the ability to protect potential T-cell epitopes from degradation before MHC-loading [9,22]. Thus, we next studied whether TB10.4 and BCG vaccines differed with regard to cellular uptake at the local draining LN (dLN), as it could be speculated that uptake into different cell types could lead to different Ag processing/epitope recognition patterns which could explain some of our observations [9].…”

“…Different intracellular compartments have been shown to be responsible for processing of different epitopes from, e.g. Streptococcus pyogenes Ag [9,10,22]. If the vaccines were taken up into different intracellular compartments, this could possibly affect the epitopes presented to T cells and lead to different T-cell epitope specificities.…”

“…On the other hand, viral vaccine vectors have been shown to be ingested largely by immature DC [1], and soluble Ag formulated in cationic adjuvants such as CAF01 or IC31 are also believed to target DC [7,8]. Different types of APC have different mechanisms of Ag uptake, different pH levels in lysosomal compartments, express different protein degrading enzymes and differ in their ability to process and cross-present Ag to MHC class I molecules [9]. Even within the same type of APC, Ag uptake and intracellular transport may vary depending on the size and nature of the Ag/pathogen [1,9].…”

Carbon nanotube-protein carriers enhance size-dependent self-adjuvant antibody response to haptens

“…One of the key steps in the immunization process is the phagocytosis of the antigen by professional antigen-presenting cells (APCs), such as macrophages, dendritic cells, 50 and certain B cells. [1,2] Once internalized by APCs, the antigen is processed into short peptide fragments. The presentation of these peptides by major histocompatibility complex (MHC) class II molecules can activate helper T cell responses that ultimately lead to the proliferation of plasma and memory B cells and to the production of high-affinity antibodies.…”