Ff. Hou et al., Phenotypic and functional characteristics of macrophage-like cells differentiated in pro-inflammatory cytokine-containing cultures, IMM CELL B, 78(3), 2000, pp. 205-213
Previous studies have demonstrated an infiltration of monocytes and increas
ed levels of IL-1 beta and TNF-alpha in some chronic inflammatory tissues.
Interleukin-1 beta and TNF-alpha are capable of protecting monocytes from s
pontaneous apoptosis and thus maintain their viability in vitro. To study t
he possible effects of these cytokines on the differentiation and function
of recruited monocytes, a model has been developed in which monocytes isola
ted from human peripheral blood were differentiated into macrophages in ser
um in the presence or absence of IL-1 beta or TNF-alpha. Monocytes cultured
with IL-1 beta and TNF-alpha underwent substantial changes in morphology,
similar to those observed in monocytes undergoing differentiation into macr
ophages. The cultured cells increased in size and vacuolization and their c
ontent of acid phosphates increased 10-fold. Although they exhibited the mo
rphological characteristics of macrophages, monocytes matured in the cytoki
nes differed functionally from those cultured in serum in a lower expressio
n of HLA-DR, lower ability for triggering the proliferation of allogeneic l
ymphocytes, higher expression of mannose receptor and greater production of
superoxide and TNF-alpha. This data suggests that IL-beta and TNF-alpha di
rect monocyte differentiation into macrophages with a reduced antigen-prese
nting and an increased pro-inflammatory factor-releasing phenotype. Elevate
d levels of IL-beta and TNF-alpha in the inflammatory tissues may therefore
not only prolong the survival of recruited monocytes, but maintain them in
an inflammatory state.