- Blood cells are produced in the bone marrow. In a normally functioning bone marrow, the blood‑forming stems cells either create more stem cells, or divide and transform into either a myeloid cell or a lymphoid cell, (Figure 1).
- Normal myeloid cells become one of the three types of lymphocyte cells:
- B-lymphocytes (B-cells) that make antibodies to invading organisms.
- T-lymphocytes (T-cells) that destroy invading organisms and cells that have become cancerous.
- Natural killer cells (NK‑cells) that attack cancer cells and viruses.
Figure 1 Development of stem cells in the bone marrow
Source: Leukaemia Care
- In ALL, the large numbers of leukaemia cells begin to accumulate in the bone marrow (Figure 2).
Figure 2 Bone marrow in ALL with numerous lymphocyte leukaemia cells
 |
Limited cytoplasm
|
There are two main subtypes of ALL. They are:
- B-cell ALL which occurs in 75% of adults
- T-cell ALL which occurs in 25% of adults
- Since the treatments used for B-cell ALL and T-cell ALL are similar, the information in this e-learning module applies to both types.
