Biological variation of serum canine calprotectin concentrations as measured by ELISA in healthy dogs.

Calprotectin is a useful biomarker of inflammation in dogs. However, the biological variation of serum canine calprotectin is unknown. Indices of biological variation were determined in serial serum samples (n=147) from 11 healthy dogs (males/females: 4/7, median age: 5 years): analytical (3.0%), intra-individual (29.9%), and inter-individual variation (33.2%), reciprocal index of individuality (1.1), and index of heterogeneity (4.9). Serum calprotectin concentrations measured by ELISA and by the previous radioimmunoassay were highly correlated, but a constant and proportional bias exists between both assays. A de novo ELISA-reference interval (RI) for serum calprotectin concentration was established (0.6-11.8mg/L). Moderate changes in serum calprotectin (minimum critical difference: 6.4mg/L) between sequential measurements are needed to be considered relevant, and a population-based RI may or may not be appropriate for serum calprotectin.

Diversity in the preimmune immunoglobulin repertoire of SHR lines susceptible and resistant to end-organ injury.

We used next-generation sequencing to identify immunoglobulin heavy chain (IGH) genetic variation in two closely related hypertensive rat lines that differ in susceptibility to end-organ disease (SHR-A3 and SHR-B2). The two SHR lines differ extensively at the IGH locus from the rat reference genome sequence and from each other, creating 306 sequence unique IGH genes. Compared with IGH genes mapped in the rat reference genome sequence, 98 are null gene alleles (31 are null in both SHR lines, 45 are null in SHR-A3 only and 23 are null in SHR-B2 only). Of the 306 divergent gene sequences, 126 result in amino acid substitution and, among these, SHR-A3 and SHR-B2 differ from one another at the amino acid level in 96 segments. Twelve pseudogenes in the rat reference genome sequence had changes displacing the stop codon and creating probable functional genes in either or both SHR-A3 and SHR-B2. A further five alleles that encoded functional rat reference genome sequence genes or open reading frames were converted to pseudogenes in either or both SHR-A3 and SHR-B2. These studies reveal that the preimmune immunoglobulin repertoire is highly divergent among SHR lines differing in end-organ injury susceptibility and this may modify immune mechanisms in hypertensive renal injury.