Cation-induced aggregation of cat Tamm-Horsfall glycoprotein and its possible role in feline urolithiasis

Importance of carbohydrate in the interaction of Tamm‐Horsfall protein with complement 1q and inhibition of classical complement activation

Tamm-Horsfall protein (THP) binds strongly to complement 1q (C1q), a key component of the classical complement pathway. The goals of this study were to determine whether THP altered the activation of the classical complement pathway and whether the carbohydrate portion of THP was involved in this glycoprotein's binding to C1q and alteration of complement activation. The ability of THP to prevent complement activation in diluted serum or plasma incubated at 37 degrees C was assessed using both a haemolytic assay with antibody-sensitized sheep RBC and a C4d ELISA. Both these methods showed that THP inhibited activation of the classical complement pathway in a dose-dependent manner. Glycosidases were used to remove most of the carbohydrate from THP. This partially deglycosylated THP bound human IgG with a higher affinity (KD1 = 1.4 nmol/L; KD2 = 0.31 micromol/L) than did intact THP (KD1 = 33.4 nmol/L; KD2 = 31.0 micromol/L). An ELISA showed that removal of carbohydrate from THP reduced, but did not eliminate, the ability of this protein to inhibit binding of C1q to intact THP. Haemolysis assays using antibody-sensitized sheep RBC showed that removal of THP carbohydrate eliminated the ability of THP to protect against complement activation. In conclusion, THP inhibited the activation of the classical complement pathway that occurred in diluted serum or plasma. The carbohydrate moieties of THP appeared to be important in this inhibitory activity.

Virulence of fungal spores determined by tracheal inoculation of goats following inhalation of aerosolized sterile feedyard dust

OBJECTIVE

To compare the virulence of spores of 7 fungi by tracheal inoculation of goats following exposure of goats to an aerosol of sterilized feedyard dust. Animals-54 weanling Boer-Spanish goats.

PROCEDURE

A prospective randomized controlled study was conducted. There were 7 fungal treatment groups, a tent control group, and a pen control group (n = 6 goats/group). Goats in the 7 treatment and tent control groups were exposed to autoclaved aerosolized feedyard dust for 4 hours in a specially constructed tent. Goats in the 7 treatment groups were then inoculated intratracheally with 30 mL of a fungal spore preparation, whereas tent control goats were intratracheally inoculated with 30 mL of physiologic saline (0.9% NaCI) solution. These treatments were repeated each week for 6 weeks.

RESULTS

Severity of pathologic changes differed significantly among the 7 fungal treatment groups as determined on the basis of gross atelectatic and consolidated lung lesions and histologic lesions of the lungs. Descending order for severity of lesions was Mucor ramosissimus, Trichoderma viride, Chaetomium globosum, Stachybotrys chartarum, Aspergillus fumigatus, Penicillium chrysogenum, and Monotospora lanuginosa. Trichoderma viride spores were the most invasive and were isolated from the bronchial lymph nodes and thoracic fluid of all 6 goats administered this organism. Spores were observed-histologically in lung tissues harvested 72 hours after inoculation from all treatment groups.

CONCLUSIONS AND CLINICAL RELEVANCE

4 of 7 fungal spore types induced significantly larger lung lesions, compared with those induced by the other 3 spore types or those evident in control goats.

Tamm-Horsfall glycoprotein binds IgG with high affinity

Tamm-Horsfall protein (THP), a monomeric glycoprotein (M(r) 80 to 100 kDa), is produced by the mammalian kidney's thick ascending limb of Henle cells and excreted into the urine. The function of THP is uncertain. Here we report that a high molecular weight contaminant in sheep THP (sTHP) preparations was identified as sheep IgG by its positive reaction with donkey anti-sheep IgG antibody and with protein G. To answer the question of whether sTHP and sheep IgG co-purified because of a physical interaction between the two proteins, an enzyme-linked immunosorbent assay (ELISA) using immobilized sTHP and soluble sheep IgG was performed. Analysis of the ELISA data identified the presence of two sets of binding sites: a high affinity site (Kd 10(-8) to 10(-9) M) and a lower affinity site (Kd 10(-6) to 10(-7) M) [corrected]. The ELISA detected a similar high affinity interaction between human THP (hTHP) and human IgG. The binding of sheep IgG to immobilized sTHP was inhibited by soluble sTHP. These observations suggest an additional factor to be considered in studies addressing THP's potential immunoregulatory function.