Ch. 12 leukocyte development, kinetics and function

What is the last granulocyte in the maturation sequence able to undergo mitosis? a.Myeloblast b.Promyelocyte c.Myelocyte d.Band

ANS C The myelocyte is the last granulocyte in the normal maturation sequence that can undergo mitosis. The myeloblast and promyelocyte precede the myelocyte; both can and do undergo mitosis. The band cell is no longer able to replicate its deoxyribonucleic acid (DNA) and so does not undergo mitosis.

Lymphocytes become transformed when they are: a.Being stimulated by an antigen b.Undergoing mitosis c.Dying d.Moving to secondary lymphoid tissues

ANS: A Transformation of lymphocytes occurs in response to antigenic stimulation. This leads to proliferation of the stimulated lymphocyte (or lymphocytes) in lymph nodes.

B cells and T cells are subgroups of what cell type? a.Monocytes b.Lymphocytes c.Macrophages d.Plasma cells

ANS: B These are both subgroups of lymphocytes.

16. Which cell is capable of phagocytosis and antigen processing? a.Band neutrophil b.Segmented neutrophil c.Macrophage d.Lymphocyte

ANS: C The macrophage can phagocytize a large variety of substances, from molecules to cells. It also plays a critical role in antigen processing for lymphocyte recognition and stimulation of lymphocyte transformation.

What directs the mitosis and maturation action of progenitor neutrophil cells in the bone marrow? a.Erythropoietin b.The number of stem cells c.The number of mature cells in the peripheral circulation d.Colony-stimulating cytokines

ANS: D Colony-stimulating cytokines bind to receptors on progenitor cells to direct them to undergo mitosis and to mature to identifiable neutrophil precursor cells. Erythropoietin is the primary cytokine for red cell development. Neither the number of stem cells nor the number of mature cells in circulation function in this role.

What substances in segmented neutrophils are important for intracellular killing of bacteria? a.Alkaline phosphatase and halides b.Myeloperoxidase and superoxide c.Collagenase and hydrogen peroxide d.Acid phosphatase and anions

ANS: B Bacteria killing is a complex mechanism, requiring activation of the neutrophil, ingestion of the bacterium, and incorporation into a phagosome. Cytoplasmic granules fuse with the lysosome and dump their contents. Myeloperoxidase, halides, hydrogen peroxide, and the formation of superoxide and oxygen radicals are all instrumental for killing. Also critical for killing is activation of proteinases such as cathepsin G.

Which cells are normally produced in multiple sites including the bone marrow, thymus, and spleen? a.Monocytes b.Lymphocytes c.Eosinophils d.Basophils

ANS: B Lymphocytes are produced in all the sites mentioned. All the others are produced only in the bone marrow.

CD34 is an antigen found on which one of the following cells? a.Myeloblast b.Segmented neutrophil c.Eosinophil d.Lymphocyte

ANS: A CD34 is found on the myeloblast and also the promyelocyte, but it is downregulated as the cell continues to mature and is not found on mature cells of any lineage.

What pool of cells is the first to arrive when extra granulocytes are needed in the tissues? a.Those that are marginating b.Those that are freely circulating c.Those from the bone marrow d.Those from the lymph nodes

ANS: A Marginated granulocytes are granulocytes clinging to the sides of small venules. They freely exchange with granulocytes in the circulating pool but can readily move into tissue along a chemotactic gradient when needed.

Which of the following cells is described as a large cell with abundant cytoplasm containing minute granules, lacy chromatin, and an indented or curved nucleus? a.Monocyte b.Macrophage c.Lymphocyte d.Basophil

ANS: A The description fits that of a monocyte. This is a transition cell found in blood; it becomes a macrophage once it enters tissue.

A cell having a round nucleus with delicate chromatin, prominent nucleoli, and scant basophilic cytoplasm with a possible rare azurophilic granule is an accurate description of a: a.Myeloblast b.Myelocyte c.Metamyelocyte d.Band

ANS: A The description fits that of a myeloblast. Often the myeloblast is agranular (without any visible granules), although special cytochemical staining can demonstrate the presence of myeloperoxidase in the cytoplasm even when granules are not present or visible.

What pools of leukocytes are included in the typical white blood count? a.All cells inside the blood vessel b.Only cells freely circulating c.Only cells marginating against the vessel wall d.All leukocytes in the body

ANS: B The clinician performs the white blood cell (WBC) count by counting the number of white cells in blood. However, a pool of granulocytes exists that is marginated (clinging to the sides of small blood vessels). Even though they are still in the blood vessel, these granulo- cytes are not freely circulating and are not counted. Only freely circulating white cells of all types are counted.

Select the correct maturation sequence for granulocytes starting with youngest. a.Promyelocyte, myeloblast, metamyelocyte, myelocyte, segmented b.Myeloblast, promyelocyte, myelocyte, metamyelocyte, band, segmented c.Segmented, band, metamyelocyte, myelocyte, promyelocyte, myeloblast d.CFU-GEMM, promyelocyte, metamyelocyte, myelocyte, segmented

ANS: B The correct maturation sequence is myeloblast, promyelocyte, myelocyte, metamyelocyte, band, segmented.

21.Why is the bone marrow storage pool of granulocytes so large compared with the total number found in peripheral blood? a.They prefer bone marrow to peripheral blood. b.They can be quickly released when needed to fight bacterial infection. c.It enhances their ability to function. d.It prolongs their life span in circulation.

ANS: B The storage pool of granulocytes in the bone marrow is composed primarily of mature segmented neutrophils and a smaller number of bands. These cells are fully functional and can be readily released to peripheral blood when needed in response to infection.

What is the primary function of leukocytes as a whole? a.Make antibodies b.Engulf bacteria c.Kill parasites d.Defend body from nonself agents

ANS: D Each white cell plays a different primary role in defending the body against nonself agents. Granulocytes are the primary defense against bacteria; eosinophils kill parasites; and plasma cells, which are fully differentiated B cells, make antibodies.

Which of the following is a feature of a normal segmented neutrophil? a.Basophilic cytoplasm b.Round nucleus with fine chromatin c.Small pink-lilac granules d.Prominent primary granules

ANS: C Segmented neutrophils contain many small pink-lilac granules in their cytoplasm. The nucleus is characterized by clumped chromatin, usually with segments, although it may appear twisted or folded. The background color of the cytoplasm is colorless; no ribonucleic acid (RNA) is present (and so no basophilia).

What is the earliest morphologically identifiable cell in the granulocyte maturation sequence? a.Pluripotent stem cell b.Colony-forming unit-granulocyte, erythrocyte, monocyte, and megakaryocyte (CFU-GEMM) c.Myeloblast d.Myelocyte

ANS: C The earliest cell that can be identified by morphology, using Wright stain, as belonging to the granulocyte maturation sequence is the myeloblast. The pluripotent stem cell and the CFU- GEMM are identified by various receptors present on the cell membrane using monoclonal antibodies and flow cytometric techniques. The myelocyte is a later stage of development than the myeloblast.

13. A segmented neutrophil performs all of the following except: a.Chemotaxis b.Phagocytosis c.Mitosis d.Pinocytosis

ANS: C The segmented neutrophil does not undergo mitosis.

Which of the following has the most controversial morphologic identification system? a.Progenitor cells b.Stem cells c.Promyelocytes d.Bands

ANS: D At least three systems exist for morphologic identification of band neutrophils. They vary with the shape of the nucleus. Hematology analyzers that perform automated differentials classify them (bands) with polymorphonuclear (segmented) neutrophils; therefore many laboratories now use the same criteria when identifying cells using the microscope.

What is the earliest stage of maturation where a neutrophil can be distinguished from an eosinophil? a.Myeloblast b.CFU-GEMM c.Metamyelocyte d.Myelocyte

ANS: D Eosinophil granules differentiate the eosinophils from the neutrophil at the early myelocyte stage. Before this, the myeloblast and promyelocyte stages are indistinguishable by morphol- ogy.

Allergies are associated with an increase of which type of granulocyte? a.Promyelocytes b.Band neutrophils c.Segmented neutrophils d.Eosinophils

ANS: D Eosinophils increase in an allergy.

Which of the following neutrophils is capable of chemotaxis? a.Stem cell b.Progenitor cell c.Myelocyte d.Band

ANS: D The band neutrophil is capable of chemotaxis (i.e., it can move along a chemical gradient). It is an almost mature polymorphonuclear neutrophil, and has full motility, active adhesion properties, and some phagocytic ability.

Which cells are responsible for antibody production? a.Macrophages b.Monocytes c.Neutrophils d.Plasma cells

ANS: D The terminally differentiated B cell is the plasma cell; its function is to make and secrete specific antibody.