Cancer Immune Therapy Edited by G. Stuhler and P. Walden ...

6.4.4
Macrophages
6.4. Phenotypic and Functional Characteristics of Immune Cells Present at the Tumor Site
Fig. 6.7 Kaplan±Meier survival curves generated
by multivariate analysis. Overall survival of
132 patients with oral carcinoma according to
the S-100 expression on tumor-infiltrating DC
and z chain expression in TIL. The numbers of
DC were determined by microscopic counts of
immunostained tumor sections: 1 = low numbers
of S-100 + DC; 2 = intermediate numbers of
S-100 + DC; 3 = high numbers of S-100 + DC. TIL
were defined based on immunocytochemistry as
follows: 0 or 1 = cells with no or low z expression;
and 2 = cells with normal z expression.
Lines A±D identify groups of patients assigned
to each category as indicated in the inset. Reproduced
with permission from Reichert et al. Cancer
2001; 91: 2136 ±2147. © American Cancer
Society/Wiley-Liss, Inc.
Macrophages (CD14 + ) are commonly found in human tumors and are referred to as
tumor-associated macrophages (TAM). While normal macrophages are APCs which
play an important role in control of infections, TAM are re-programmed to inhibit
lymphocyte functions through a release of specific cytokines, prostaglandins or reactive
oxygen metabolites (ROM). It is hypothesized that re-programming of TAM occurs
in the tumor microenvironment as a result of tumor-driven activation [75]. Evidence
has accumulated indicating that invasiveness of tumors, e. g. human primary
colon carcinomas, is directly related to the number of TAM detected in the tumor
[76]. In invasive breast cancer, an increased TAM count is an independent predictor
of reduced relapse-free survival as well as reduced overall survival [77]. The available
data support the active role of TAM in tumor-induced immunosuppression, on the
one hand, and in the promotion of tumor growth, on the other. The mechanisms
that contribute to TAM-mediated inhibition of immune cells are probably numerous,
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