Complement

A reference for interpreting complement tests in rheumatology. It starts from the pattern (low C3 and C4, low C4 with normal C3, low C3 with normal C4, absent CH50 or AH50, or raised levels), then sets out what each pattern points to, the next test to send, and the prognostic weight of low complement in SLE, cryoglobulinaemia, Sjögren’s disease, IgG4-related disease, ANCA vasculitis and antiphospholipid syndrome. It also covers inherited deficiency, laboratory pitfalls and the complement inhibitors now in use.

Trillions of microorganisms live on your skin, in your mouth and in your gut, and almost none of them cause harm. Episode 1 of the immunology series asks what makes the rare one dangerous: the four kinds of pathogen, why damage rather than species or number defines the line between commensal and pathogen, the three host strategies, and the four layers of defence and how fast each one acts.

Final 24-month data from APPLAUSE-IgAN: the oral factor B inhibitor iptacopan roughly halved the rate of eGFR decline in high-risk IgA nephropathy (−3.10 vs −6.12 ml/min/1.73 m²/year) and cut hard kidney-failure events from 33.5% to 21.4%, converting an accelerated approval based on proteinuria into evidence on preserved kidney function — with serious infection the trade-off to manage.