The results of this study establish that monocyte adhesion, which undoubtedly is responsible for many substantial changes in the monocyte, is not essential for monocyte survival and differentiation to a macrophage-like cell. As monocytes and their dfferentiated forms are found, not only in the extra cellular matrix, but also in suspension in the blood and the peritoneal fluid, this can help to understand their function under these circumstances. Many details have been revealed for the different monocyte subsets. This study gives now further substance for the hypothesis that the CD16+ monocytes are a more mature subset, differentiated in the blood under the influence of M-CSF. Moreover, MMAC have as a unique feature the upregulation of both, phagocytosis and T cell stimulatory capacity, two functions that usually are not up-regulated in parallel. Whether this new macrophage type has its own place in the MPS, or it stands for another possible phenotype of a chameleon like cell type, known as the macrophage, remains to be elucidated.