The relative composition of the inflammatory infiltrate as an additional tool for synovial tissue classification.
OBJECTIVE
Traditionally, differences in absolute numbers of cells expressing a certain marker (e.g., positive staining cells per mm²) have been used in immunohistological synovial tissue classification. We have begun to evaluate the relative composition of the inflammatory infiltrates, i.e. percentages of inflammatory cell types in inflammatory infiltrates, as an alternate classification tool that may potentially improve tissue diagnostics, subgrouping in clinical trials, and understanding of pathogenesis of inflammatory and noninflammatory arthropathies.


METHODS
Synovial tissue specimens (normal synovium, n=15; orthopedic arthropathies, n=6; osteoarthritis, n=26; early undifferentiated arthritis, n=10; rheumatoid arthritis, n=26; chronic septic arthritis, n=11) were stained for CD15, CD68, CD3, CD20, and CD38. Densities of cells expressing a given marker were determined in the superficial subintima. Binary and multicategory receiver operating characteristic (ROC) analysis and naïve Bayes classifier were used to compare the abilities of (1) the absolute densities of cells expressing a given marker (absolute method) with (2) the percentages of these cells in the inflammatory cell population (relative method) to differentiate among the six tissue classes.


RESULTS
The inflammatory infiltrates in normal synovium and the orthopedic arthropathies consisted almost exclusively of CD68+ and CD3+ cells. Notable fractions of CD20+ and CD38+ cells appeared in a subset of osteoarthritis samples, and increased further in early, rheumatoid and chronic septic arthritis. ROC analyses and naïve Bayes classifier ranked the absolute method above the relative method in terms of overall discriminatory ability. The relative method became slightly superior when the samples were also stratified according to the total number of inflammatory cells/mm².


CONCLUSIONS
This exploratory investigation featuring a variety of joint disorders revealed that measuring the relative proportions of inflammatory cell types may aid in synovial tissue classification if the samples are also stratified according to the intensity of inflammation.
Department of Cellular Proteomics, Helmholtz Centre for Infection Research, Braunschweig, Germany.
Cristina
C
Della Beffa
Elisabeth
E
Slansky
Claudia
C
Pommerenke
Frank
F
Klawonn
Jialiang
J
Li
Lie
L
Dai
H Ralph
HR
Schumacher
Frank
F
Pessler
D051997:ADP-ribosyl Cyclase 1 / Q000032:analysis / Q000276:immunology; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000032:analysis* / Q000276:immunology; D018951:Antigens, CD20 / Q000032:analysis / Q000276:immunology; D001168:Arthritis / Q000276:immunology* / Q000473:pathology*; D001499:Bayes Theorem; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013583:Synovial Membrane / Q000166:cytology / Q000276:immunology* / Q000473:pathology*; D055815:Young Adult
D015703:Antigens, CD; D018951:Antigens, CD20; D051997:ADP-ribosyl Cyclase 1