166 J. Øvrebø Bohnhorst et al. counting for 50%, immunemediated disease 40% and neoplasia 10% of cases with diag- nosed causes of FUO. Dunn & Dunn (1998) sorted 101 dogs with FUO into 6 main groups with the following re- sult: infections 16%, neoplasia 9.5%, immune- mediated disease 22%, miscellaneous condi- tions 11.5%, primary bone marrow ab- normalities 22%, and true FUO 19%. In the present study we have investigated the occurrence of selected auto antibodies and 2 in- ﬂammatory mediators, interleukin-6 (IL-6) and tumour necrosis factor (TNF-α) in serum from dogs with fever that we eventually diagnosed as immune-mediated. The criteria for being included into the material was fever above 39.9 °C that did not respond to 2 successive treatments with different antibi- otics, but to a subsequent prednisolone cure. Materials and methods Dogs The material consisted of 20 dogs of 13 differ- ent breeds. All dogs were brought to the clinic within 3 days after they became ill. They were submitted to general clinical examinations, and separated into 3 groups based on clinical signs (Table 1). One group showed only fever, while the others who showed muscle pain and muscle and joint-pain, respectively. Dogs included in the latter 2 groups were stiff and lame. Pain could commonly be located in the M. triceps brachii and M. quadriceps femoris, and in the elbow, carpal, stiﬂe or tarsal joints. Neck stiff- ness and pain were also observed, but not as single sign. The fever was measured to lie be- tween 39.9 and 41.4 °C . Blood specimen was drawn from a cephalic vein and serum was prepared and kept frozen at -20 °C till the analyses were performed. The pa- tients were ﬁrst treated with phenoxymethyl- penicillin and secondly trimetoprim /sulphadi- azin in adequate doses, 2-3 days with each, Acta vet. scand. vol. 43 no. 3, 2002 without clinical effect. Then they got pred- nisolone, starting with 1mg/kg/day and tapered down during a period of 2-3 weeks. Forty-four healthy dogs of 7 different breeds and 2 mongrels taken to the clinic for vaccina- tion, served as controls. The breeds represented were border collie (12), bullmastif (1), cavalier King Charles spaniel (1), English setter (3), golden retriever (1), Gordon setter (21), Irish soft coated wheaten terrier (2) and riesen- schnauzer (1). The sex distribution was 22 fe- male and 22 male, and the mean age was 4 year, ranging between 1 and 12. Serum analyses The methods applied for detection of canine auto antibodies were locally modiﬁed variants of routine human diagnostical techniques and established as part of a C. Sc. Dissertation (un- published). The techniques were worked out by use of a collection of 500 sera from dogs of dif- ferent breeds with a variety of symptoms of mainly rheumatic, autoimmune and febrile dis- ease conditions and with 45 sera from healthy dogs as controls. The sera were partly collected locally and partly provided by Kjerstin Thoren- Tolling and Solveig Knagenhjelm, The Norwe- gian College of Veterinary medicine, Oslo, Norway. Antinuclear antibodies (ANA) were detected by use of the indirect immmunoﬂuorescence (IIF) technique using Hep-2 cells ﬁxed in alcohol as antigen substrate (Miller et al. 1985). The cells were cultivated in the laboratory and dispersed into Terasaki plates for application in the test.The sera were screened for ANA reac- tivity at a 1:20 dilution in PBS and the reaction visualised by a FITC conjugated Fc-speciﬁc goat anti-dog IgG (Cappel research Products, Durham, NC) at dilution 1:60. The serum dilu- tion 1:20 was chosen on the basis of positive re- actions in 70/230 sera (31.3%) from dogs mainly with signs of systemic disease and 0/45