Table 1.
Innate immune cells in the skin and their role in leishmanial disease (Leish)
| Cell type | General function | Observations in murine Leish | Observations in Leish in vitro |
|---|---|---|---|
| Keratinocytes | Sensors of injury & infection | - | Source of IL-10, associated with PKDL[111] |
| Location: epidermis | |||
| Langerhans cells | Antigen presentation in certain infections | Uncertain, not necessary for induction of Th1 responses[33] | Correlation between high LC density and acute cutaneous L. tropica disease[112] |
| Location: epidermis | Induction of peripheral tolerance | ||
| Th2 induction | |||
| Cross priming of naïve CD8+ T cells | |||
| Dermal DC | Immune surveillance | Sensors of infection[33] | - |
| Location: dermis | Antigen presentation | ||
| Cross presentation to CD8+ T cells | |||
| Dermal macrophages | Antimicrobial activity and production of pro- and anti-inflammatory mediators | Can act as host cells [8,32] | Host cells (non-human primate skin)[6] |
| Location: dermis | |||
| Plasmacytoid DC | IFNα production | Leishmania loaded pDC can induce protective immunity[113] | - |
| Location: dermis | Activation of NK cells, B cells T cells and myeloid DC cells | ||
| Mast cells | Regulating later Inflammatory response by Neutrophils | Sentinels, contribute to DC recruitment[114] Tissue pathology[115] | Elevated numbers in MCL lesion[117] |
| Location:Dermis | Susceptibility[116] | Possibly an association with wound healing[118] | |
| Monocyte derived | Inflammatory cells | Induction of protective immunity[7] | Species dependent production of IL-12, co-stimulation[36] |
| Inflammatory DC | T cell stimulation Production of IL-12, iNOS and TNFα | Primary cells harboring parasites in later stages of disease development (healing mice)[28] | |
| Location: Inflamed dermis | |||
| Neutrophils polymorph nucleated cells (PMN) | Uptake and destruction of pathogens | Temporary early major host cells facilitating L. major infection[8] | *Human PMN can kill promasitigotes and amastigotes.[14] |
| Silent Transfer of parasites into macrophages[13] | |||
| Location: dermis | Protective[16] | Found in lesions[18,20] | |
| Tissue pathology – in later stages of disease[22,23] | Can harbor parasites in VL[9] | ||
| NK cells | Early source of IFNγ | Contribute to early resistance against the parasite[37,119] | Associated with protection and cure[43,45] |
| Location: Inflamed dermis |
The general functions of cells have been adapted from Nestle et al.[110]