Immunophenotypic Characteristics of Normal Mature BCells

Many studies have been reported, in which the phenotypic features of normal, mature PB (25,28,31), and/or BM B-cells (32-36) have been analyzed. These studies systematically show that virtually all PB and a substantial part of BM B-cells are mature sIg+ lymphocytes. Most of these correspond to naive sIgM+/sIgD+ (80-90%) and, to a lesser extent (10-15%), immature sIgM+ B-lymphocytes (37-43). In contrast, sIgM+, sIgG+, or sIgA+ memory B-cells only represent a minor fraction of the total sIg+ lymphocytes (<10%) (28). These different B-cell populations have in common expression of cytoplasmic CD79a and surface CD19, CD79b, CD21, CD22, FMC7/CD20, CD37, CD40, CD44, CD21, CD18, CD53, and CD81, and they are strongly positive for surface CD45 and cytoplasmic bcl2 (8,25,28,44-48); in contrast, they are negative for CD10 and CD103 (25,44-48). Other antigens like CD5, CD23, CD24, CD27, CD38, CD11c, CD25, CD43, CD62L, CD80, and CD148 show variable expression within the sIg+ mature PB and/or BM B-cells (32-36). Based on these latter markers, several different subsets of normal mature PB and/or BM B-cells can be identified. As an example, expression of both CD27 and CD148 have been shown to identify the population of memory B-cells generated by germinal center reaction (39-41); among these memory B-cells both Ig class-switched sIgG+ or sIg A+ B-cells and either sIgM+ or sIgM+/sIgD+ memory B-lymphocytes are included (39-41).

Table 1

Incidence and Type of the Most Common Aberrant Phenotypes Detected in Leukemic B-Cell Chronic Lymphoproliferative Disorders Other Than CLL

Incidence of aberrant phenotypes (%) 80

SMZL

Type and frequency of the most common aberrant phenotypes (% in parentheses)11

Antigen overexpression

Asynchronous antigen expression

Aberrant FSC/SSC

CD22-/+(weak)/CD5+ (100) CD22-/+(weak)/CD10- (100) CD22-/+(weak)/sIg+ (68) CD22-/+(weak)/FMC7+ (64)

PLL, prolymphocytic leukemia; HCL, hairy cell leukemia; LPL, lymphoplasmacytic lymphoma; MCL, mantle-cell lymphoma; FL, follicular lymphoma; SMZL, splenic marginal zone B-cell lymphoma; FSC, forward light scatter; SSC, sideward light scatter (flow cytometry). Present in more than 50% of cases within each group.

Table 2

Phenotypic Subsets of Mature Peripheral Blood (PB) and Bone Marrow (BM) B-Cells From Normal Healthy Adults

PBa BM3

Table 2

Phenotypic Subsets of Mature Peripheral Blood (PB) and Bone Marrow (BM) B-Cells From Normal Healthy Adults

PBa BM3

sIg-/CD22+(weak)/CD23- CD10+

ND

4.9-46

CD11c- CD19+ FSC/SSC(int) (precursor B-cells)

sIg+ CD19+ FSC/SSC(int) (mature naive/memory B-cells)

97-

100

53.9-95.1

SIg M+/D-

1.3-4.3

5-60

Slg M+/D+

71

-90

NR

SIg G+ or A+

0.8-

36.9

NR

CD5+

2.5-43

6.3-49.2

CD11c+

4.6-

39.5

0.8-11.7

CD19+/CD20+ or ++/CD22+

97-

100

53.9-95.1

CD23+

11.7

-83.9

4-63.1

CD24+ or ++

92

-97

98-100

CD25+

5.4

-44

0.8-12

CD27+

31.9

-89.4

NR

CD38+ or ++

74

-88

84.5-99.5

CD43+

8-

21

NR

CD62L+

24

-52

NR

CD80+

10

-22

NR

CD103+

0

-6

0

FMC7+

64.2-98

51-88.2

CD10-/CD11c++/FMC7++/CD22++

0.3

-6.8

0.3-9.2

CD103-/CD25-/CD5-/CD23-/CD19++/FSC/SSC(hi) (mature memory B-cells)

CD103-/CD25-/CD5-/CD23-/CD19++/FSC/SSC(hi) (mature memory B-cells)

^Results expressed as the range (minimum-maximum) of the percentage of the total B-cells. ND, not detected (constantly < 0.001%); NR, not reported; int, intermediate lymphoid FSC/ SSC values; hi, high lymphoid FSC/SSC values; -, negative; +(weak), weakly positive; +, positive; ++, strongly positive.

Although for those markers showing a variable expression on mature sIg+ B-cells, the percentage of positive cells depends on the sensitivity of the method used for their evaluation; an estimation of their relative representation on PB mature B-cells is shown in Table 2.

Until now, information on the exact phenotypic features of mature B-cells from lymphoid tissues, as assessed by flow cytometry-based methods for the quantitative evaluation of antigen expression, has been scanty. Even so, recent studies based on the analysis of reactive lymph nodes show that germinal center and mantle zone-derived normal B-cells display clearly different phenotypes (4) (Table 3). Accordingly, germinal center B-cells are usually negative for CD5, CD23, and cytoplasmic bcl2, they express sIg of the IgG subtype and they are strongly positive for CD20, CD10, CD38, and the Ki67 proliferation-associated nuclear antigen. In addition, these cells are CD27+, which supports the notion that they would correspond to memory B-cells (37). In contrast, normal B-cells derived from the mantle zone of the lymphoid follicles are typically sIg M/D+, bcl2+, and CD23+, and display lower reactivity for CD38 and CD20 and variable CD5 expression, in the absence of positivity for CD10 and CD27 (49). This phenotype suggests that mantle zone B-cells would correspond to naive B-cells. In addition, these latter B-cells usually

Table 3

Phenotypic Differences Between Germinal Center and Mantle Zone Normal B-Cells Derived From Reactive Lymph Nodes

CD5 CD10 CD20 CD23 CD27 CD38 cy-bcl2 Ki67 sIgG sIgM/D

Germinal center-derived - ++ ++ - + ++ - ++ +(weak) -

normal B-cells

Mantle zone-derived -/+ - +(weak)/+ + - +(weak)/+ + -/+(weak) - +

normal B-cells

-, negative; +(weak), weakly positive; +, positive; ++, strongly positive; Cy, cytoplasmic.

show negativity or low reactivity for Ki67, supporting the notion that they would correspond to resting B-lymphocytes.

Was this article helpful?

0 0

Post a comment