User:Tomas Machacek/sandbox

Ducks
The records on cellular immune response to T. regenti in ducks are rather scarce. Cell infiltration of affected skin sites in repeatedly infected ducks was only noted, however, lacking further characterization of the infiltrating cells. In the CNS, eosinophils and heterophils surround the parasite but do not prevent its migration towards the final localisation in the nasal mucosa.

Considering antibody response, anti-cercarial IgM culminates 15 DPI, while anti-cercarial IgY reaches a peak 30 DPI. Ducks infected at higher age have higher anti-cercarial IgY levels than those infected at lower age. However, the anti-cercarial IgY levels are not largely dependant on the infection dose. Several parasite antigens recognized specifically by host IgY are considered as candidates for immunodiagnostics.

Mice
The infection manifests as early type I hypersensitivity reaction and a late phase cutaneous inflammation.

Cellular immune response is represented by production of pro-inflammatory (IL-1β, IL-6 and IL-12p40) and anti-inflammatory (IL-10) cytokines in a skin of mice infected for the first time. Lymphocytes from their skin draining lymph nodes exhibit mixed Th1/Th2 polarization after exposure to parasite antigens. On the contrary, anti-inflammatory IL-4 and IL-10 dominate in mice infected repeatedly which also secrete large amounts of histamine from mast cells. Lymphocytes from their skin draining lymph nodes produce IL-4 and IL-5 after stimulation with parasite antigens which shows Th2 polarization of host immune response. (Kolářová 2004, JIM)

In a spinal cord, strong cellular immune response consisting of granulocytes, plasma cells, macrophages, and T-cells develops in immunocompetent mice especially around the damaged schistosomula. CD3-deficient mice develop no or just mild inflammation which is accompanied by neurological symptoms due to mechanical damage caused to the nervous tissue (Kolářová et al. 2001, Kouřilová et al. 2004b, Lichtenbergová et al. 2011). Activated microglia are localised in the migratory tracks of schistosomula and in the inflammatory lesions containing parasite residues. Therefore, they were suggested to take part in schistosomula destruction either alone or in cooperation with macrophages and T-cells (Lichtenbergová et al. 2011). Hypertrophied astrocytes are located in the migratory tracks and in the proximity of the schistosomula which implies their role in immune response and tissue reparation (Lichtenbergová et al. 2011). Murine astrocytes and microglia were shown to produce pro-inflammatory cytokines (IL-6 and TNF-α) and nitric oxide after in vitro exposure to parasite antigens, which supports their role in host immune response.

IgM antibody response targets mainly carbohydrate epitopes of parasite molecules. High levels of IgG1 and IgG2b, but no IgG2a, specific to mostly protein epitopes of cercarial homogenate are detectable as long as 150 DPI in repeatedly infected mice. The level of total IgE increases as soon as 10 DPI and remains high up to 150 DPI in reinfected mice. (Licht) Increased production of antigen-specific IgG1 and total IgE, but slight decrease in antigen-specific IgG2b corroborate Th2 immune polarization in repeatedly infected individuals. (Licht, Kouř JIM)

Human
Clinical manifestation of human immune response to T. regenti infection is known as cercarial dermatitis (aka swimmer's itch). It is regarded as a neglected allergic emerging disease. Majority of humans (82% of adults, 57% of children) who have experienced cercarial dermatitis (caused by undetermined species of bird schistosome) have increased levels of T. regenti antigen-specific IgG, but not IgE. Cercarial homogenate and excretory-secretory products of T. regenti induce basophils from humans without a history of cercarial dermatitis to degranulate and release IL-4.