Type IV hypersensitivity in the pathogenesis of FIPV-induced lesions.

In focal lesions of feline infectious peritonitis (FIP), the cells involved in the delayed-type hypersensitivity were identified in formalin-fixed paraffin-embedded and frozen samples taken from 35 affected cats. The clinical diagnosis of FIP was confirmed by necropsy, histology and direct immunofluorescence against the coronaviruses on cryostatic sections. The immune cells were detected immunohistochemically by the Avidin-Biotin-Complex (ABC) method using either polyclonal antibodies against lymphoid antigens (CD3) or monoclonal antibodies against lymphoid (PAN-T, CD4, CD8) and myeloid antigens (MAC387). Better identification of T cells and macrophages was found on formalin-fixed paraffin-embedded sections than on cryostatic ones, while T lymphocyte subpopulations could be differentiated only in cryostatic sections. Type IV hypersensitivity was detected in focal feline infectious peritonitis virus (FIPV)-induced lesions from progressive activation of T lymphocytes, mainly CD4+, and the presence of granulocytes and macrophages. The FIPV-induced lesions could be studied as examples of granulomas caused by unconventional antigens, such as viruses or immune complexes.

Clinical and immunological effects of immunotherapy with alum-absorbed grass allergoid in grass-pollen-induced hay fever.

A double-blind, placebo-controlled study of immunotherapy was conducted in 19 patients with grass-pollen hay fever to evaluate the efficacy and safety of a formalinized depot grass allergoid. The patients were assessed before and during IT by clinical (symptom-medication scores during the grass- pollen season, specific nasal and skin reactivity) and immunological (specific IgE, IgG, IgG1 and IgG4 antibodies) parameters. High doses of grass allergoid, corresponding to a cumulative pre-seasonal dosage of 46,050 PNU, were administered, with only one systemic reaction. The actively treated patients had significantly lower symptom-medication scores than placebo (p less than 0.01) during the month of May and showed a significant decrease in specific skin (p less than 0.01) and nasal (p less than 0.05) reactivity, and a significant early increase in specific IgE (p less than 0.01), IgG (p less than 0.0005), IgG1 (p less than 0.001) and IgG4 (p less than 0.05), with a subsequent decrease of IgE and IgG1. No differences were detected in any of these parameters in the placebo group. A correlation was found between high IgG4/IgG1 ratio and the specific skin reactivity decrease (r = 0.691, p less than 0.05), whereas a high IgG4/IgG1 ratio was associated with higher symptom-medication scores (r = 0.654, p less than 0.05). Possible explanations of these apparent discrepancies are proposed.