DIARECT Newsletter No. 3/2007

Almost two years after the introduction of recombinant Ro/SS-A (60 kDa) Prof. Humbel's laboratory in Luxembourg has carried out a comparative analysis. To this end 93 patient sera that were positive for Ro/SS-A or La/SS-B in immunofluorescence and immuno dot blots were measured in an ELISA using Ro/SS-A from three different sources: two native proteins from calf thymus and DIARECT recombinant antigen.
The results of these studies clearly demonstrate that all three antigens are virtually identical. All clearly positive sera determined using immunofluorescence and dot blots were also clearly positive in ELISAs with each antigen. As can be expected, some sera react slightly differently when their calculated units were compared.
Also interesting is the result of an investigation of 96 sera that were clearly ANA positive (HEp-2 cell), but were negative in antigen-specific immuno-dots using Ro/SS-A 60 kDa and La/SS-B. All of these sera were also negative when tested using the three different Ro/SS-A (60 kDa) antigens. Curiously one sera was positive, but with the recombinant 52-kDa protein.
If you would like to convince yourself of the specificity and sensitivity of recombinant Ro/SS-A (60 kDa) antigen, you can take advantage of our Medica offer. From now until December 31, 2007, you can receive a one-milligram evaluation sample at 50% off the regular price.

Nine years ago, DIARECT was established with the goal of supplying you with high-quality, dependable autoimmune antigens. For us quality includes high sensitivity, low background and above all high lot-to-lot consistency. We showed you one example of our superior lot-to-lot reproducibility in Newsletter No. 3-2005 using Tissue Transglutaminase (tTG). Now 5 years after the first lot of tTG was produced we are pleased to present you with data showing the stability of the protein upon storage at -70°C. As you can see, there is no difference between the lot produced in 2002 upon analysis with our standard QC procedures five years later. In addition, reactivity now compared with a recent lot is virtually indistinguishable. As part of our ongoing commitment to quality, we are currently evaluating all of our antigens that we have been offering for the past five years.