Differentiation of rodent immune and hematopoietic system reactive lesions from neoplasias

Abstract

The immune and hematopoietic systems play an important role in the normal homeostasis of blood and blood cells and for immune responses to endogenous and exogenous processes and insults. In order to interpret histopathologic changes in the immune and hematopoietic systems, it is important to understand the normal anatomy and histology of the thymus, spleen, lymph nodes, bone marrow, and other tissues. The thymus, spleen, and lymph nodes can be categorized by anatomical compartments, each of which contributes to specific immune functions. Lesions may be diagnosed by interpretive or descriptive (semiquantitative) methods. The interpretation of these tissues by lesion in anatomical compartments should allow for better understanding of these reactions and more definitive pathologic findings. Proliferative lesions may be difficult to differentiate from lymphomas and leukemias. The use of immunohistochemistry, compartmental pathology, and methods for the evaluation of clonality will make interpretation easier.

FIGURE 1

Thymus of an eighteen-month-old B6,129 mouse showing nodular medullary hyperplasia.

FIGURE 2

Thymus of another eighteen-month-old B6,129 mouse with medullary hyperplasia and CD3 expression in T-cells. Note that there is loss of CD3+ lymphocytes in the medullary hyperplasia.

FIGURE 3

Thymus of an eighteen-month-old B6,129 mouse with medullary hyperplasia showing CD45R expression. Note the increase in CD45R+ B cells in several areas.

FIGURE 4

A much enlarged mandibular lymph node of a mouse with ulcerative skin lesions. There is loss of normal nodal architecture. Most of the node contains mature plasma cells.

FIGURE 5

Greatly enlarged spleen of a mouse infected with Plasmodium berghei ten days previously.

FIGURE 6

Spleen of mouse infected with P. berghei ten days earlier. The red pulp is expanded with prominent erythroid hyperplasia, and the white pulp has marked germinal center and plasma cell hyperplasia.

FIGURE 7

Spleen in a malaria-infected mouse with numerous plasma cells. Immunohistochemistry for human κ light chains expressed mostly in the plasma cells.

FIGURE 8

Enlarged rat spleen with myeloid and erythroid hyperplasia.

FIGURE 9

Enlarged rat spleen with myeloid and erythroid hyperplasia also has many plasma cells expressing IgG. Immunohistochemistry for rat IgG.

FIGURE 10

Enlarged spleen of a mouse with early stage murine acquired immunodeficiency syndrome showing hyperplasia of the white pulp.

FIGURE 11

High magnification of previous figure of a mouse with murine acquired immunodeficiency syndrome showing a heterogeneous population of plasmacytoid cells, immature and mature plasma cells.

FIGURE 12

Spleen of a mouse with later stage murine acquired immunodeficiency syndrome showing many centroblasts with mitotic figures.

FIGURE 13

Greatly enlarged lymph nodes of a six-month-old C3H/lpr mouse with lymphoproliferative disease.

FIGURE 14

C3H/lpr mouse with lymphoproliferative disease. A monomorphic population of medium-sized T-cells is seen.

FIGURE 15

Spleen of a twenty-four-month-old C57BL/6NCr mouse with one enlarged white pulp area (upper left), which represents an early follicular lymphoma.

FIGURE 16

Normal splenic white pulp with many mature lymphocytes (centrocytes) in the eighteen-month-old C57BL/6NCr mouse from Figure 15.

FIGURE 17

White pulp of the mouse in Figure 15 showing early follicular lymphoma containing a mixed population of centroblasts and centrocytes, including cells with cleaved nuceli.

FIGURE 18

Spleen of a B6C3F1 mouse with early follicular lymphoma in one large white pulp area. There is a loss of dense cellular CD45R expression in the early lymphoma.