As many as six subsets of DCs have been described in mice including mDCs and pDCs which are also found in Both DC types are professional antigen presenting cells (APCs) but differ in some other functional aspects. For example, mDCs and pDCs differ not only in phenotypic markers but also in functional properties. mDCs are more frequently found and secret high levels of  during antigen presentation. pDCs have the unique ability to produce high levels of IFN-alpha in response to antigen structures and may, therefore, play an important role in innate antiviral immunity. erhans cells, dermal DCs and plasmacytoid DCs.

The different subtypes of mouse DC share a common capacity to presetn antigens to T cells and to promote cell-cycle progression. However, they differ in the other aspects of DC-T cell signalling that determine the subsequent fate of the T cells that they activate. For example, CD8+ DCs induce a Th1 biased cytokine response in reactive CD4+ T cells, whereas CD8- DCs tend to induce a Th2 biased response. The main factor in this difference is the much higher level of IL-12p70 produced by Cd8+ Dcs under experimentla conditions.

Mouse DCs that are classified as “mature” express CD11c (the integrin-? chain) and the co-stimulator molecules (CDE80, CD86 and CD40) and have moderate to high surface levels of MHC II, although the levels of all of these can be further elevated on activation. These features always correlate with a striking ability to induce the proliferation of allogeneic T cells.

Surprisingly, the T cell markers CD4 and CD8 are expressed on mouse DCs and are useful for segregating subtypes. CD8 on DCs is in the form of an ??-homodimer rather than the ??-heterodimer that is typical of T cells. So far there is no evidence that either marker is functionally significant on mouse DCs. 

Other markers that are useful for segragating mouse DC subtypes include CD11b (the integrin ?M chain of Mac-1) and the interdigitating DC marker CD205 (the multilectin domain molecule DEC205, origianlly known as NLDC-145.

Lymphoid and myeloid DCs differ in phenotype, localization, and function. Both subsets express high levels of CD11c, class II MHC, costimulatory molecules CD86 and CD40. Tod ate, the most reliable amrker to distinguish these two subsets is CD8?, which is expressed as a homodimer on the lymphoid DC, but is absetn from the myeloid subset.

In mouse lymphoid organs there are at least 6 DC subpopulations. These are

• CD8- (which can be divided into 2 or more subsets on the basis of the absence or presence of the CD4 expression marker);

• CD8int;

• CD8+ DCs; The CD8 subtype, formerly designated as the lymphoid DC subset, have been suggested as being involved in the induction of Th1 responses as well as in the induction of tolerance to peripheral self-antigen.

• Langerhans cells;

• dermal DCs;

• plasmacytoid DCs.

In the spleen: splenic DCs express similar amounts of CD11c, class II MHC, costimulatory molecules CD80, CD86 and CD40, but can be subdivided into 3 subtypes on the basis of their expression of CD4 and the CD8? homodimer.

• CD8?-CD4-

• CD8?-CD4+ and

• CD8?+CD4-.

CD8- DCs, whether they express CD4 or not induce a vigorous proliferative response in CD4+ T cells. In contrast, CD8+ DCs induce a limited CD4+ T cell response that is associated with marked T cell apoptosis. This death is due to interaction of Fas on activated T cells with Fas ligand (FasL) on DCs. Similarly, Cd8?+ DCs induce much less IL2 production by CD8 T cells then do CD8?- DCs, leading to lower proliferation. These observations suggested that CD8?+ DCs could play a role in the feedback mechanisms aimed at controlling ongoing immune responses.

The CD8+ DCs are concentrated in the T cell areas. The CD8- DCs are concentrated in the marginal zones of most laboratory mice. However, the CD8- DCs migrate into the T cell zones on stimulation with microbial products.

In the Thymus: In the thymus, two distinct subsets have been identified on the basis of CD8? expression.

In the Lymph Nodes: In lymph nodes a large population of cells is negative for CD4 and CD8? and two smaller populations are either CD4+CD8?- or CD4-CD8?+.