CD2 and acute lymphoblastic leukemia: Initially, four main T-ALL subtypes were proposed: mature (sCD3 positive), cortical (CD1a+), pre-T (cCD3+ plus CD2+, CD5+, and/or CD8+), and pro-T ALL (cCD3+ and CD7+); however, with the integration with RNA-microarrays, the T-ALL subtypes began to be better characterized [153,154,155].