Complexity of dendritic cell subsets and their function in the host immune system

Abstract

Dendritic cells (DCs) are professional antigen-presenting cells that are critical for induction of adaptive immunity and tolerance. Traditionally DCs have been divided into two discrete subtypes, which comprise conventional and non-conventional DCs. They are distributed across various organs in the body and comprise a heterogeneous population, which has been shown to display differences in terms of surface marker expression, function and origins. Recent studies have shed new light on the process of DC differentiation and distribution of DC subtypes in various organs. Although monocytes, macrophages and DCs share a common macrophage-DC progenitor, a common DC progenitor population has been identified that exclusively gives rise to DCs and not monocytes or macrophages. In this review, we discuss the recent advances in our understanding of DC differentiation and subtypes and provide a comprehensive overview of various DC subtypes with emphasis on their function and origins. Furthermore, in light of recent developments in the field of DC biology, we classify DCs based on the precursor populations from which the various DC subsets originate. We classify DCs derived from common DC progenitor and pre-DC populations as conventional DCs, which includes both migratory and lymphoid-resident DC subsets and classify monocyte-derived DCs and plasmacytoid DCs as non-conventional DCs.

Figure 1

Differentiation of dendritic cells (DCs) from haematopoietic stem cells (HSC). The HSCs differentiate into common lymphoid progenitors (CLPs) and common myeloid progenitors (CMPs); CMPs subsequently differentiate into monocytes and pre-DCs in the bone marrow. Subsequently, monocytes and pre-DCs enter the blood and migrate to lymphoid organs and peripheral tissues, where they give rise to lymphoid DCs and tissue-resident DCs. In addition to CMPs, CLPs also have the potential to give rise to DCs, but their contribution is not well understood.

Figure 2

Classification of dendritic cell (DC) subsets as conventional and non-conventional DCs. Conventional DCs are derived from common DC progenitor and pre-DC populations and are further divided into migratory and lymphoid DCs. Non-conventional DCs include plasmacytoid DCs, which are derived from the pre-DC population along with monocyte-derived DC subsets, and are found in various peripheral organs.