Skin thickness score in systemic sclerosis: an assessment of interobserver variability in 3 independent studies.

OBJECTIVE: Using data from 3 independent studies, to quantify the interobserver reliability of semi-quantitative skin scoring methods (the original and the modified Rodnan skin thickness scores) used to assess the degree and extent of cutaneous thickening in systemic sclerosis (SSc). METHOD: Interobserver variability of the original Rodnan skin thickness score method (cutaneous thickness assessed in 26 body surface areas using a 0-4 scale) was evaluated in one study. The modified Rodnan method (cutaneous thickness assessed in 17 body surface areas using a 0-3 scale) was evaluated in 2 studies. In all 3 studies, each patient's skin thickness was assessed by 6 or 7 observers in a blinded fashion. RESULTS: The overall within patient standard deviations were not statistically different in all 3 studies (5.4, 4.6 and 4.6) irrespective of the overall mean skin thickness scores (26.6, 18.3 and 17.7). With the original Rodnan technique, the within patient standard deviation tended to be higher in patients with higher skin thickness scores. In the 2 studies which used the modified technique, no significant differences in within patient standard deviation were noted between high and low skin thickness scores. CONCLUSIONS: Three independent studies demonstrate that the Rodnan skin thickness scoring techniques are reproducible among different observers (the within patient standard deviation being consistently about 5 units). Our data provide valuable information needed for sample size calculations for SSc trials in which skin thickness score is an outcome variable.

Null cell identification and characterization with OKT16: an anti-p40 monoclonal antibody.

A murine monoclonal antibody, OKT16, specific for human lymphocytes of T lineage, was isolated by standard immunization and hybridization techniques. The distribution of the antigen defined by OKT16 was similar to the antigen reactive with monoclonal antibodies 3A1 and WT1. This identity of antigen targets was confirmed in an enzyme-linked immunosorbent assay system and by sequential immunoprecipitation. Under reducing conditions, OKT16 reacted with an antigen of 40K daltons; however, under nonreducing conditions this antigen appeared as an 84K-dalton molecule, which suggests that the p40 antigen exists as a disulfide-linked dimer. By indirect immunofluorescence, OKT16 reacted with a greater fraction of nonrosetting, non-B (null) lymphocytes than with antibodies to other T cell-specific proteins. Two-color immunofluorescence demonstrated the coexpression of the T16 antigen and the C3bi receptor on most null cells. The T10 antigen (found on cortical thymocytes and activated peripheral T cells) was restricted to most T16-bearing null cells and expression of the Fc receptor for aggregated IgG (defined by monoclonal antibody 73.1) was restricted to a major subset of T16-bearing null cells. The T cell-specific markers defined by OKT8, OKT11, and OKT17, as well as the monocyte marker defined by OKM5, were expressed by smaller subsets of OKT16-reactive null cells. These studies support by phenotypic analysis the functional heterogeneity ascribed to null cells. The 40K-dalton T16 antigen has the most extensive null cell representation of all the T lineage markers described to date.

Distinct classes of human T-cell activation antigens.

The characterization of three groups of antigens expressed by activated human T lymphocytes and detected by monoclonal antibodies is reported. Antigens defined by OKT19, OKT21, and OKT22 do not appear on in vitro activated T cells until increases in DNA synthesis become apparent and are not detected on most Interleukin 2 (IL-2)-independent cell lines and normal peripheral blood lymphocytes, monocytes, and granulocytes. Cell surface molecules reactive with the monoclonal antibodies OKT23 and OKT24 are displayed prior to any notable increase in DNA synthesis and are present on IL-2 independent cell lines, irrespective of lineage. T23 and T24 do not appear on peripheral blood cells and their distribution more closely resembles that of the T9 antigen (the receptor for transferrin) than antigens of the other groups. The third group of antigens, T14 and T20, have been classified as "early" antigens relative to DNA synthesis. They are expressed by distinct populations of normal lymphoid cells as well as by some IL-2-independent cell lines. Display of each group of activation antigens on T lymphocytes can be induced by either phytohemagglutinin, purified protein derivative from tuberculin, or allogeneic non-T cells, is not restricted to the OKT4+ or OKT8+ subsets, and is predominant on cells exhibiting the light-scattering properties of blast cells. The relative lack of expression of these antigens among normal peripheral blood cells make them attractive candidates for identifying changes in the status of immune activation.

Patterns of antigenic expression on human monocytes as defined by monoclonal antibodies.

A series of seven monoclonal antibodies directed at determinants on human peripheral blood monocytes were produced and characterized. The antibodies were separated into three groups based on cell distribution and percentages of monocytes bearing antigen. Hybridoma antibodies, termed OKM1, OKM9, and OKM10, recognized antigen(s) expressed on the majority of adherent monocytes, null cells, and granulocytes. The second group, comprising OKM5 and OKM8, reacted with most adherent monocytes and platelets. OKM3 and OKM6, comprising a third group of antibodies, reacted with a subpopulation of adherent monocytes and platelets. OKM antibodies were not expressed on lymphocytes, thymocytes, and lymphoblastoid cells, with the exception of OKM3 which reacted with three B-cell lines. SDS gels of immunoprecipitates formed with OKM antibodies yielded the following tentative molecular weight results: OKM1 and OKM9 antigens appeared to be 160,000 (nonreduced) and 170,000 (reduced); OKM10 precipitated two polypeptides of 170,000 and 115,000 (reduced); OKM5 and OKM8 precipitated a single polypeptide of 88,000 (reduced, nonreduced); OKM6 antigen appeared to be 116,000 (nonreduced) and 130,000 (reduced).

Classification of human lymphocytes and monocytes with the OK series of monoclonal antibodies.

Membrane antigens expressed by either peripheral blood B cells, monocytes, or activated T cells have been identified by monoclonal antisera. OKB1, OKB2, OKB4, and OKB7 react with all or most circulating Smlg+ cells and have differential effects on the generation of plaque forming cells in the reverse hemolytic plaque assay. Of the new monocyte antibodies, OKM5 displays more restricted specificity for monocytes than the previously described OKM1, whereas OKM3 and OKM6 define monocyte subsets. In addition, several new T-cell "activation" antigens have been identified that differ in their expression depending on the nature of the triggering stimulus. These reagents should be of diagnostic and perhaps therapeutic utility.