George Moxley

Tryptase Precursors Are Preferentially and Spontaneously Released, Whereas Mature Tryptase Is Retained by HMC-1 Cells, Mono-Mac-6 Cells, and Human Skin-Derived Mast Cells

Tryptase (α and β) levels in serum are used to assess mast cell involvement in human disease. Using cultured cells, the current study examines the hypothesis that protryptase(s) are spontaneously secreted by mast cells at rest, whereas mature tryptase(s) are stored in secretory granules until their release by activated cells. HMC-1 cells have only β-tryptase genes and the corresponding mRNA. Mono-Mac-6 cells have both α- and β-tryptase genes but preferentially express α-tryptase. Mono-Mac-6 cells spontaneously secrete most of their tryptase, which consists of α-protryptase, whereas mature tryptase is retained inside these cells. HMC-1 cells also spontaneously secrete most of their tryptase, identified as β-protryptase, and retain mature tryptase. Skin-derived mast cells retain most of their tryptase, which is mature, and spontaneously secrete protryptase(s). Total tryptase levels in plasma are detectable but no different in healthy subjects with and without the gene for α-tryptase, consistent with pro forms of both α- and β-tryptase being spontaneously secreted. Thus, protryptase(s) are spontaneously secreted by resting mast cells, whereas mature tryptase is retained by mast cells until they are activated to degranulate.

Sexual dimorphism in innate immunity.

OBJECTIVE To establish whether variation in innate immunity, as measured by the level of tumor necrosis factor (TNF) in lipopolysaccharide (LPS)-stimulated whole-blood culture, is related to sex or HLA. METHODS Normal volunteers (72 women, 159 men) completed questionnaires and donated peripheral blood specimens. Blood samples were exposed to LPS in a 4-hour in vitro culture, and supernatants were then tested by sandwich-type immunoassay measuring TNF levels. Statistical techniques included multivariate analysis and maximal-likelihood modeling of allelic effects. RESULTS Both male and female groups showed substantial within-group variation (coefficient of variation 59.1% for women, 40.3% for men). However, the mean +/- SD LPS-stimulated TNF level in the female group was nearly 30% lower than in the male group (1,556+/-919 pg/ml versus 2,203+/-889 pg/ml; P < 0.0001, unadjusted for covariates). Sex was independent of any microsatellite marker allele of TNF (covariate-adjusted increment of 785 pg/ml from female to male sex; P < 0.0001). In multivariate modeling of the female group, the LPS-stimulated TNF level was not independently influenced by menstrual cycle phase, oral contraceptive use, or plasma estradiol level. Allelic modeling showed that significant TNFab microsatellite allelic effects existed (P = 0.002 versus model omitting allelic effects). The female group showed a significantly downward deviation from mean TNF level with TNFa4b5 (-903 pg/ml deviation from the overall mean) and an upward deviation with TNFa10b4 (598 pg/ml). The male group showed significantly higher-than-mean levels with TNFa1b5 (909 pg/ml), TNFa5b7 (1,191 pg/ml), and TNFa6b5 (332 pg/ml). Thus, the two sex groups differed in which of their TNFab marker alleles showed significant deviations from the overall mean. CONCLUSION Female subjects have a nearly 30% lower innate immune response, stemming largely from influence independent of the HLA-region TNF locus and without further independent variation stemming from plasma estrogen level.

Genetic studies, clinical heterogeneity, and disease outcome studies in rheumatoid arthritis

HLA haplotypes influence various clinical RA features considered to reflect severity in case-control and cohort studies. Of particular note is the fact that HLA generally influences the development of erosive and sometimes seropositive and nodular disease; in prospective studies, it noticeably affects joint surgical intervention. These are valuable clues indicating that HLA influences RA severity and chronicity. Nevertheless, HLA influences are generally weak enough so as to require large study subject numbers for detection. As a result, HLA genotyping has restricted usefulness for prediction of clinical severity in individual patients.

Response to comments in: Statin use is associated with reduced incidence and progression of knee osteoarthritis in the Rotterdam study by Clockaerts et al.

We thank Clockaerts et al for their thoughtful commentary on our paper and will address a number of their comments. They expressed concern regarding lack of verification of our data related to statin use, duration of use and dosage, and indicated these data were based on self-report. While we acknowledged in our paper1 that we did not have dosage data, the verification was that participants brought their medications with them during yearly follow-up visits and we were able to confirm that statins were prescribed for these patients. This approach was not as valid as a pill count but, in our view, is more rigorous than self-report. Clockaerts et al accounted for duration of statin use by examining effects for those with 1–119 days, 120–364 days and 365 days or greater of statin use at 50% or more of the recommended daily dosage. Our approach was to use the yearly follow-up visit prescription data indicating 0, 1, 2, 3 or 4 years of statin use to examine the effects on changes in …