Immune mechanisms in humanSarcoptes scabiei(Acari: Sarcoptidae) infestations

Abstract

Scabies is a parasitic infestation of human and animal skin caused by different strains of the itch mite, Sarcoptes scabiei. The World Health Organization (WHO) has declared scabies in human as a neglected tropical disease, and today over 200 million people worldwide are affected. The two most commonly reported clinical manifestation of the condition are ordinary (OS) and crusted scabies (CS). CS, which can lead to fatal consequences due to secondary bacterial infections, is mostly observed in immunocompromised subjects but can also, although rarely, be detected in immunocompetent individuals. Innate and adaptive immune system components are involved in protection and pathogenesis of scabies, although with some differences between OS and CS. While the cutaneous immune response is dominated by CD4 + T-cells in OS, it is mainly mediated by CD8 + T-cells in CS. The two clinical conditions also differ in CD4 + T-cell-mediated immune responses with mixed T H 1/T H 2 (protective) and T H 2/T H 17 (non-protective) immunoprofiles in OS and CS, respectively. Moreover, the development of CS is associated with early immunosuppression that is followed by deleterious immune response to uncontrolled mite proliferation. However, the immune response to scabies still needs further attention due to inconsistent results in the literature. The aim of this study is to attract more attention to this area by summarizing the current literature on innate and adaptive immune responses triggered against S. scabiei mites.

The local skin cellular immune response determines the clinical outcome of sarcoptic mange in Iberian ibex (Capra pyrenaica)

“…In humans, the more severe crusted scabies is associated with fewer macrophages infiltrating the skin and an unbalanced Th1/Th17 immune response, whereas in ordinary scabies, M2 macrophages are more abundant in the inflammatory infiltrate, indicating a balanced Th1/Th2 immune response ( 26 ). Both a suppressive effect mediated by a macrophage migration inhibitory factor expressed by S. scabiei and/or an induction of mixed M1/M2 macrophage polarization against the scabies mite have been suggested to explain the lower macrophage counts and shift to the M2 phenotype in scabietic humans ( 54 – 56 ).…”

“…Thus, the higher initial (26 dpi) T lymphocyte count of the totally recovered ibexes ( Figure 6 ), leading to lower total cell, macrophage (both total and the M2 phenotype), T lymphocyte, and plasma cell counts at the end of the study period (103 dpi) than in the terminal ibexes ( Figures 3 – 6 , 8 ), seems to confirm that an initial effective local skin T-cell immune response is crucial for controlling the spread of sarcoptic mange in Iberian ibex. Further characterization of this T-cell immune response, including the cell types, cytokines, and gene expression involved, should help us to fully understand the pathophysiological and immune mechanisms responsible for the control or extension of sarcoptic mange in Iberian ibex ( 21 , 24 – 26 , 49 , 50 , 54 ).…”

Scabies: Immunopathogenesis and pathological changes

“…Both immediate (type I) and delayed (DTH or type IV) hypersensitivity responses are involved (Walton et al 2008 ; Bhat et al 2017 ). Although the exact role of cell-mediated and humoral host immune responses in the pathogenesis of OS and CS remains largely unknown, it is now well established that clinical severity of the disease depends on variations in the type and amplitude of the associated cellular and humoral responses (Gazi et al 2022 ).…”

“…Although the exact role of CD8 + T cells in CS is unspecified, they may induce tissue damage by exhibiting direct cytotoxicity against keratinocytes and/or releasing cytokines, which could enhance the inflammatory response targeting resident skin cells (Hay et al 2012 ; Bhat et al 2017 ; Gazi et al 2022 ). Th17 cells are another major subset of T-cells that share in the pathogenesis of CS by recruiting and activating neutrophils at sites of inflammation.…”

Case of concurrence of bullous pemphigoid and Norwegian scabies

“…Scabbing scabies are mainly caused by the loss of CD8 + T lymphocytes, eosinophils, a small number of macrophages and B cells. 8,9 Bullous scabies is easily confused with BP. Its clinical manifestations in patients are tension bullae and oedematous erythema.…”