T LUNG¹, K MATOZAN¹, M RISCH¹, L RISCH¹, U NYDEGGER<sup>1

1</sup>labormedizinisches zentrum Dr. Risch, Waldeggstrasse 37, 3097 Liebefeld bei Bern

Introduction. With three pathways, 48 activation and control proteins and their fragments,
9 protein complexes and 12 receptors, measured w/v and/or by functional activity, the contribution of the complement system to big data is considerable. Complement analytics until recently were impeded by short expiration of test kits and tedious haemolytic assays ; functional CH50&AP50-like assessment in ELISA format is now possible by measuring the capacity of the terminal C5b-9 (membrane attack complex, MAC) and the factor B-properdin bond to assemble. We now use the WIESLAB® CP310 classical pathway EIA test. It combines principles of the functional haemolytic assay for complement activation with the use of specific antibodies for a neo-epitope expressed by the formation of MAC (LOINC® code 4524-5) ; other approaches, e.g. the one from WAKO diagnostics use an automated liposome immunoassay with an enzyme release procedure. Such a dodging of haemoglobinometry allows to reduce coefficients of variation and improve standardisation in exploring a patients’ capacity to lyse bacteria and other cells.
The now well delineated complement gene family, containing C2, C3, C8A, C8B, CFH, CFHR5, CFI and ITGB2. Inclusion of complement analytics in genetic risk prediction for diseases with genetic glitch is thus possible. In addition, complement analysis is now seen by clinicians in perspective with other types of analyses-->acute phase proteins, immunoglobulins, vitamins.
Methods. Immunoassays involving nephelometry were used to quantitate C4&C3 and Ig in fasting blood sera of 1470 apparently healthy subjects >60 yrs. 25(OH) vitamin D was quantitated with the high-performance liquid chromatography (HPLC).
Results&Discussion. First experience with the CP310 test will be outlined on a poster. With the SENIORLAB study (ISRCTN registry no. 53778569) we put w/v concentrations of C4, C3 and immunoglobulin (Ig) levels into perspective with serum vitamin D levels. Low levels of 25(OH)D were positively associated with IgG2 and C4 (the lower vitamin D, the lower C4) yet inversely related to levels of IgG1 and IgA and C3. Acute phase complement proteins related to C-reactive protein (CRP) evolve in parallel during inflammatory states and prods type 2 diabetes, lipid metabolism and atherosclerosis. Complement testing can validate the effect of certain treatments, which in the wake of the beneficial effects of eculizumab (Soliris®, Alexion) are opening up a wider array of complement system targeting drugs now under evaluation : C1INH in trials on sepsis (NCT01766414) and ischaemia-reperfusion injury (NCT01886443).

References:
Reis ES, Mastellos DC, Yancopulou D et al
Applying complement therapeutics to rare diseases.
Clin Immunol 2015 ; 161 : 225-240
Sakem B, Nock C, Stanga Z et al
Serum concentrations of 25-hydroxyvitamin D and immunoglobulins in an older Swiss cohort: results of the Senior Labor Study.
BMC Medicine 2013 ; 11 :176.
https://ghr.nlm.nih.gov/geneFamily/complement