Final answer:
All B-cells in acute lymphoblastic leukemia express the cellular marker CD19, which is used for diagnosis and classification of the disease through methods like flow cytometry or immunohistochemistry. This contrasts with conditions like agammaglobulinemia, which involves a block in B-cell maturation due to lack of Bruton tyrosine kinase (Btk).
Step-by-step explanation:
All B-cells in acute lymphoblastic leukemia (ALL) express a cellular marker known as CD19, among others. In the context of acute lymphoblastic leukemia, this cellular marker helps in the diagnosis and classification of the disease. Physicians often use immunophenotyping, a method which involves flow cytometry or immunohistochemistry, to detect the presence of these cellular markers on the surface of leukemic cells. An accurate assessment of the types of markers expressed by the leukemic cells is critical for the determination of the specific type of leukemia and for guiding treatment options.
Acute lymphoblastic leukemia is characterized by an overproduction of immature leukocytes, which are B-cell precursors expressing CD19. Unlike a related condition known as agammaglobulinemia, where a deficiency in Bruton tyrosine kinase (Btk) leads to a block in B-cell maturation at the pre-B-cell stage, in ALL, the B-cells are malignant and proliferate uncontrollably. Moreover, immunoglobulin production is affected, leading to an impaired immune response. The fact that ALL involves immature leukocytes distinguishes it from chronic leukemia, where there is an accumulation of mature leukocytes.