Blood Types Explained: ABO, Rh Factor & Transfusion Compatibility
Blood type is defined by antigens on red blood cells (RBCs). Two major systems:
ABO System
- Type A: A antigens; anti-B antibodies in plasma.
- Type B: B antigens; anti-A antibodies.
- Type AB: Both A & B antigens; no anti-A/B (universal plasma donor).
- Type O: Neither antigen; both anti-A & anti-B (universal RBC donor).
Rh System
- Rh-positive: D antigen present (85% population).
- Rh-negative: D antigen absent; can form anti-D if exposed.
Combined Types (8 Common)
A+, A−, B+, B−, AB+, AB−, O+, O−
Transfusion Compatibility
| Recipient | Can Receive RBCs From |
|---|---|
| O− | O− only |
| O+ | O−, O+ |
| A− | A−, O− |
| A+ | A−, A+, O−, O+ |
| B− | B−, O− |
| B+ | B−, B+, O−, O+ |
| AB− | A−, B−, AB−, O− |
| AB+ | All types (universal RBC recipient) |