Guinea Pig Serum | Complement Source CFT | Sterile Filtered | EU Origin

Why is guinea pig serum the standard complement source for the Complement Fixation Test?

Guinea pigs have the highest total haemolytic complement activity (CH50) of all common laboratory animal species. Their serum contains high titres of all classical pathway components — C1q, C4, C2, C3, and the membrane attack complex (C5–C9) — at levels that reliably lyse sensitised sheep erythrocytes at the dilutions used in the WHO CFT protocol. The complement activity is reproducible across individual animals when pooled, and the guinea pig complement system is well characterised in terms of reaction kinetics and temperature sensitivity. Rat, rabbit, and mouse serum all have significantly lower complement titres and are not accepted substitutes for CFT complement; human serum is not used due to the presence of endogenous antibodies that would interfere with the test antigen system.

What storage conditions are required to preserve guinea pig complement activity?

Complement proteins — particularly C1q, C2, and factor B — are heat-labile and inactivated by repeated freeze-thaw cycles. For maximum complement activity, store guinea pig serum at –70 °C or below in single-use aliquots. At –20 °C, complement activity declines measurably within weeks to months depending on initial titre and freeze-thaw history. Never store at +4 °C for more than 24 hours. Thaw aliquots rapidly at 37 °C immediately before use and place on ice; discard any unused portion rather than refreezing. For CFT workflows, titrate each new lot against your sensitised sheep erythrocyte system before use to confirm the working dilution — complement titre is documented on the CoA but should be verified in your specific assay system.

How is guinea pig serum used in the Complement Fixation Test (CFT)?

In the CFT, guinea pig serum serves as the complement source in a two-stage reaction system. In the first stage, patient serum (heat-inactivated to remove endogenous complement) is incubated with test antigen in the presence of a standardised amount of guinea pig complement. If the patient’s antibodies bind the antigen, the immune complexes formed fix (consume) the complement. In the second stage, sensitised sheep erythrocytes (coated with anti-sheep haemolysin) are added. If complement was fixed in stage one (antibody present), no lysis occurs — the test is positive. If complement was not fixed (antibody absent), it remains free to lyse the sheep erythrocytes — the test is negative. The guinea pig complement must be titrated to the exact working unit (the 50% haemolytic unit, CH50) for each lot, as variation in complement titre directly affects assay sensitivity and specificity.

Can guinea pig serum be used for complement studies other than CFT?

Yes — guinea pig serum is used wherever high-titre, well-characterised complement is required. In haemolysis assays, it is the standard lytic complement in the CH50 determination and in antibody-dependent complement-mediated cytotoxicity (CDC) assays. In complement pathway research, guinea pig serum serves as a complement source for studying classical pathway activation, C3 deposition, and complement inhibitor screening. It is also used as a positive complement control in serological test kits for brucellosis, equine infectious anaemia, Maedi-Visna, and other notifiable diseases diagnosed by CFT in veterinary diagnostic laboratories. For studies requiring human-specific complement interactions (e.g., anti-drug antibody CDC assays), normal human serum is the appropriate choice — guinea pig complement should not be substituted in those assays.

What documentation is supplied with EU Origin Guinea Pig Serum, and is it available on request only?

Every order includes a Certificate of Analysis (CoA) with complement titre determination, Certificate of Origin (CoO), and Safety Data Sheet (SDS). Guinea pig serum is listed as on-request availability due to the lower collection volumes compared to larger laboratory animal species and the specific handling requirements for maintaining complement activity. Lead times and available volumes are confirmed at the time of enquiry. Batch reservation for up to 36 months is available on request for laboratories running long-term CFT diagnostic programmes or complement research projects — reserving a single validated, titred lot eliminates inter-lot complement titre variation across the duration of the study.