Embodiments of the present disclosure provide polypeptides, related materials and compositions, and methods for their use. In certain embodiments, the present disclosure provides a monomeric Tamm-Horsfall Protein polypeptide, or a biologically active truncation thereof. Other embodiments provide polynucleotides encoding a polypeptide described herein, nucleic acid expression vectors including the polynucleotides, and recombinant host cells including the expression vector. Yet other embodiments provide pharmaceutical compositions including a polypeptide described herein. Also provided are methods for treating a renal disease, disorder, or condition in a subject and/or modulating an immune response in a subject.