Fel d 4, a cat lipocalin allergen.

BACKGROUND: Cat allergy is unique among allergy to mammals in that the major allergen Fel d 1 is a uteroglobin-like protein and not a lipocalin. The biochemical spectrum of the cat allergens is thus uncertain, particularly with regard to the role that a cat lipocalin protein may play in sensitization to cats in allergic individuals. OBJECTIVE: To analyse cDNA encoding a lipocalin allergen and the corresponding recombinant allergen at both the molecular and immunological levels. METHODS: A submandibular salivary gland cDNA expression library was constructed and screened for clones producing IgE-binding polypeptides. cDNA encoding a lipocalin allergen and its corresponding recombinant allergen were analysed. RESULTS: An IgE binding molecule with high sequence identity to the boar salivary lipocalin and the horse lipocalin Equ c 1 allergen was isolated and designated, Fel d 4. Serum from 62.96% of cat-allergic subjects examined had measurable IgE antibody to Fel d 4 but typically at low levels. Despite this in 47% of sera the anti-Fel d 4 IgE titres were higher than the anti-Fel d 1 titres. IgE binding to the lipocalin allergen could be blocked by an allergen extract from cow and to a lesser degree by extracts from horse and dog. CONCLUSION: Fel d 4 is a lipocalin allergen produced by the cat, which binds IgE at relatively high frequency in cat-sensitive individuals. The allergen provides not only a means for investigating differences in the immune response to lipocalin allergens from that found for other mammalian species but also an important reagent for the diagnosis of cat allergy.

Immunotoxicity of a standardized citrus polymethoxylated flavone extract.

Polymethoxylated flavones (PMFs) from citrus inhibit production of TNF-alpha and other pro-inflammatory cytokines. As TNF-alpha also modulates NK cell activity, the current studies were conducted to assess the potential for a standardized citrus PMF mixture to suppress humoral and innate immune functions. PMFs were isolated from orange peel oil using a procedure that obtained a consistent mixture of PMFs both in identity and proportion. The mixture consisted of nobiletin (30.7%), 3,3',4',5,6,7,8-heptamethoxyflavone (27.9%), trimethylscutellarein (14.5%), tangeretin (10.4%), sinensetin (5.8%), 5-demethyl-nobiletin (2.0%), hexa-O-methylquercetagetin (1.3%), 5-demethyl-tetramethylscutellarein (0.6%), and other flavonoids (2.7%). To assess the effect of the PMF mixture on humoral immune responses, female B(6)C(3)F(1) mice (n=8) were exposed to the PMF by gavage at 5, 50, 150 and 500 mg/kg/day for 28 days. On day 25, mice were sensitized to sRBC by tail vein injection and AFC response determined 4 days later. Humoral immunity was insensitive to suppression following exposure to all concentrations of the PMF mixture. Suppression of NK cell activity was observed only following 500 mg/kg/day for 28 days. Body weights were not affected by exposure to any concentration of the PMF mixture in sRBC immunized or non-immunized mice. However, in sRBC-immunized mice, higher concentrations of PMF were associated with a statistically insignificant increase in spleen weight (P>0.05). No change in spleen weight was observed in non-immunized mice. As anticipated, based on previously published in vitro observations, long-term, high-dose exposure to a standardized mixture of citrus PMFs caused a mild suppression of NK cell activity; however, humoral immunity was not sensitive to suppression at the same exposure levels.

Reduction of responses to angiotensin II by antidepressant drugs.

The effects of the antidepressant drugs desipramine, fluoxetine and tranylcypromine and the non-antidepressant control cocaine on angiotensin II function were determined in vivo by use of angiotensin-induced drinking in rats and in vitro using contractile responses of the rat uterus. The results of the drinking studies showed that the three antidepressants, but not cocaine, reduced the dipsogenic effects of angiotensin II. In vitro, all of the drugs reduced the effects of not only angiotensin but also acetylcholine and oxytocin on the uterus. The inhibition appeared to be non-competitive in all cases. These results indicate that the antidepressant drugs reduced the activity of angiotensin II, albeit non-selectively, and suggest that the previously reported effects of antidepressants on isoprenaline-induced drinking in rats reflect an action on angiotensin activity rather than a reduction of beta-adrenoceptor activity as previously suggested.

Effect of chronic growth hormone administration on diabetic nephropathy in the rat.

Indirect data exist which implicate elevated growth hormone (GH) as a factor in the development of diabetic nephropathy. The administration of somatostatin (SRIH) has been shown to reverse many of the changes found in early diabetic nephropathy; however, it is unknown whether SRIH causes these effects by the suppression of GH or by other unspecified factors. To study directly the possible effect of excess GH in the development of diabetic nephropathy, either ovine growth hormone (0.2 mg oGH) or diluent buffer was administered IM daily for 19 weeks to diabetic rats and to controls. Severity of nephropathy was assessed by 24 hour urine albumin excretion (UAE), relative kidney weight, and kidney histology. Results showed that diabetic rats overall had elevated UAE and kidney weight vs non-diabetic rats (46.2 +/- 8.6 vs 5.4 +/- 1.3 mg per day and 5.7 +/- 0.2 vs 2.7 +/- 0.1 mg per g of body weight, respectively, p < 0.001). However, no differences were detected between diabetic rats treated with GH compared to control diabetic rats. Additionally, diabetic rats had histopathologic changes consistent with early diabetic nephropathy, but no difference in severity scores was found between diabetic groups. These data provide evidence against GH as an etiologic factor in the development of diabetic nephropathy and it is speculated by the authors that SRIH exerts its protective renal effects in diabetes by mechanisms other than GH suppression.

Effects of somatostatin and captopril on glomerular prostaglandin E2 production in normal and diabetic rats.

Somatostatin (SRIH) has recently been shown to be effective in reversing many of the early changes of diabetic nephropathy. It is unknown whether SRIH exerts its protective effects via its ability to suppress growth hormone (GH) or via other direct renal effects. Since changes in glomerular prostaglandin (PG) E2 production are thought to be an important part of the underlying pathophysiology of diabetic nephropathy, we sought to determine if SRIH altered glomerular PG E2 production in the rat. Whole glomeruli isolated from streptozotocin-diabetic rats and from controls were incubated with either saline, captopril, or varying concentrations of SRIH, and PG E2 production was determined by direct radioimmunoassay of media. Incubation with captopril (10(-4) M) resulted in equivalent increases in PG E2 production in glomeruli from both control and diabetic rats (140.8 +/- 12.8% and 150.2 +/- 18.9% respectively). Incubation with high concentrations of SRIH (10(-6) M) also resulted in significant increases in glomerular PG E2 production in both diabetic and control rats. However, at low SRIH concentrations (10(-10) M), glomerular PG E2 production was increased only in the diabetic rats (167.0 +/- 11.4% vs 95.3 +/- 9.2% in normals). We conclude that SRIH increases glomerular PG E2 production, and that glomeruli from diabetic rats appear to be more sensitive to lower concentrations of SRIH when compared to normal rats. It is possible that this effect on PG E2 production may underlie the favorable effects of SRIH on the glomerulus in diabetes.

Serum cortisol responses in febrile children.

Adrenocortical stress response in children with a variety of febrile illnesses was prospectively evaluated in 76 patients presenting to a general pediatric clinic with temperature greater than 101 degrees F (38.3 degrees C). Serum cortisol concentrations at presentation and again after recovery from infection were determined. Overall mean magnitude change in cortisol concentrations was 3.6-fold. Cortisol response was unrelated to the height of temperature but significant differences depending on clinical diagnosis were identified. The largest response (5-fold) was observed in patients with pneumonia, bacterial meningitis and fever of undetermined etiology. Current recommendations to double or triple replacement hydrocortisone dosage during times of increased stress in children with adrenal insufficiency are adequate only for simple febrile illnesses such as upper respiratory infection and streptococcal pharyngitis but could be subtherapeutic for infections such as pneumonia, meningitis and fever of undetermined origin, which imply a greater systemic involvement. It is possible, but untested, that a 4- to 5-fold increase in dosage would be more appropriate in those conditions.