Biomedical Engineering Reference
In-Depth Information
TABLE 6.11
Cells Contributing to the Hepatic Microenvironment
Cell Type
Size (
m)
Relative Percentage of Total Cells
m
Stroma
Kupffer cells
12-16
8
Vascular endothelia
11-12
9
Biliary endothelia
10-12
5
Fat-storing cells
14-18
3
Fibroblasts
11-14
7
Pit cells
11-15
1-2 (variable)
Parenchymal cells
Mononuclear (type I)
17-22
35
Binuclear (type II)
20-27
27
Acidophilic (type III)
25-32
5
Endothelial cells are associated with the vasculature found in almost all tissues. These
cells play a major role in the trafficking of cells in and out of tissue and may play a major
role in determining tissue metabolism.
Lymphocytes and neutrophils have a transient presence in tissues, typically as a part of
a host defense response or other cleanup functions.
These accessory cells are typically about 30 percent of the cellularity of tissue, while the
parenchymal cells make up the balance. An example is provided in Table 6.11 that lists
the cellularity of the liver.
EXAMPLE PROBLEM 6.6
What happens if these accessory cells are removed?
Solution
The role of accessory cells (in some cases called stromal cells) in bone marrow cultures has
been systematically studied. Since the immature cells can be isolated based on known antigens,
the relative abundance of the key parenchymal cells and the accessory cells can be varied. Such
an experiment amounts to a titration of the accessory cell activity. The results from such an exper-
iment are shown in Figure 6.28. All cell production indices (total cells, progenitor cells, and
preprogenitor cells) decline sharply as the accessory cells are removed. Supplying preformed
irradiated stroma restores the production of total and progenitor cells but not the preprogenitors.
This result is consistent with the expectation that specific interactions between accessory cells and
parenchymal cells are important for immature cells.
