Tweet 2/10 🔬 CD20 basics •Exact function: still mysterious •No natural ligand •No soluble form •Likely works as a Ca²⁺ channel •Expressed from late pre-B → mature B cell stage 👉 A perfect “window” to eliminate disease-driving B cells.

Tweet 3/10 ⚠️ But here’s the catch: CD20 is NOT expressed on: •Plasma cells (antibody factories) •Long-lived memory plasma cells (in bone marrow) 👉 That’s why rituximab depletes B cells but autoantibodies often persist.

Tweet 4/10 Although “mysterious,” evidence suggests CD20 has roles: •Linked to BCR signaling & calcium flux •Knockout humans & mice: normal B-cell development, but defective memory B cells, isotype switching, IgG production & humoral immunity •Likely needed for optimal

Tweet 5/10 So how do anti-CD20 antibodies actually work? They kill B cells by: •Apoptosis •Antibody-dependent cell-mediated cytotoxicity (ADCC) •Complement-dependent cytotoxicity (CDC) But… not all anti-CD20 drugs act the same way.

Tweet 6/10 Classification: •Type I anti-CD20 → Rituximab, Ocrelizumab, Ofatumumab •Type II anti-CD20 → Obinutuzumab Both bind CD20, but their killing style is different.

Tweet 7/10 Type I (Rituximab, Ocrelizumab, Ofatumumab) •Push CD20 into lipid rafts •Undergo FcγRIIB-mediated internalization •Rely mainly on CDC •Induce caspase-dependent apoptosis •Variable depletion → sometimes inferior in SLE

Tweet 8/10 Type II (Obinutuzumab) •Do not promote lipid raft clustering •Less internalization → CD20 stays available longer •Rely on direct cytotoxicity + ADCC •Induce lysosome-mediated apoptosis (caspase-independent) •Stronger NK-cell activation → deeper B-cell depletion

Tweet 9/10 Type I vs Type II •Type I → CDC-heavy, internalizes, weaker NK response •Type II → ADCC-driven, minimal internalization, stronger NK response 👉 That’s why Obinutuzumab often outperforms Rituximab in trials.

Tweet 10/10 So the paradox of CD20: ❓ Function unclear ✅ Yet one of the most successful immunology targets Because how we target it changes outcomes. CD20’s story is still evolving—and so are our therapies.

@IlliasulK @DrAkhilX Type II less complement dependent cytotoxicity

@IlliasulK @DrAkhilX Great question, @IlliasulK! CD20 is a surface protein found on B-cells, and while its exact function isn't fully understood, it plays a crucial role in B-cell activation and differentiation.

@IlliasulK @DrAkhilX Great question, @IlliasulK! CD20 is a B-cell surface marker that plays a pivotal role in B-cell activation and differentiation.

And still, half the cases will hover at “probable autoimmune” a trial of steroids given, swelling goes down, and the reflex is: “Let’s start MMF or RTX.” Steroid responsiveness ≠ diagnosis. Before stepping up therapy, pause. Re-biopsy, rethink, reframe. #MedTwitter

🧩 C-ANCA positive + renal dysfunction + cavitating lung lesions = Wegener’s (Granulomatosis with Polyangiitis) Key clues: • C-ANCA → PR3 antibodies • Cavitary nodules on CXR → necrotizing granulomas • Renal involvement → pauci-immune GN 💡 Always rule out infection (esp.

ايش الجواب و ليش قسم ال#hematology

Helicobacter pylori’s secret resilience: coccoid forms, yeast havens, and outer membrane vesicle release for survival and spread https://doi.org/10.1080/104084...