The reverse cholesterol transport model is widely used to explain the protective role of HDL in atherogenesis. HDL encompass structurally and functionally heterogeneous particles. Two-dimensional nondenaturing polyacrylamide gradient gel electrophoresis and subsequent immunoblotting helps to differentiate quantitatively minor HDL-subclasses from the bulk of HDL, which contains apoA-I and has electrophoretic α-mobility. Pulse-chase experiments identified the quantitatively minor HDL subclasses preβ 1 -LpA-I, γ-LpE, and LpA-IV as initial and fast acceptors of cell-derived cholesterol and α-migrating HDL (i.e. α-LpA-I) as a late and slow acceptor. In plasmas of patients with certain forms of familial HDL-deficiency such as apoA-I deficiency and Tangier disease, preβ 1 -LpA-I, γ-LpE, and LpA-IV represent the only HDL particles and account for the significant residual cholesterol efflux capacity of these plasmas. These particles however also fulfil important roles in reverse cholesterol transport of normal plasma. Preβ 1 -LpA-I, for example, is generated, during the interconversion of HDL by lipid transfer proteins. Thus incubation of plasma with phospholipid transfer protein increases the concentration of preβ 1 -LpA-I and in parallel increases the cholesterol efflux capacity of plasma indicating that lipid transfer proteins modulate cholesterol efflux by modification of HDL subclass composition.ApoE and γ-LpE are of special interest for reverse cholesterol transport since macrophages can produce apoE. We investigated the impact of apoE polymorphism on the ability of human macrophages to express apoE mRNA and secrete apoE. A reverse transcription-polymerase chain reaction assay with a competitive internal RNA standard did not identify genotype-related differences in apoE mRNA expression in unloaded cells. Under this condition apoE3/3 cells secreted approximately two-fold more apoE than cells which did not express apoE3. Loading with acetyl-LDL led to genotype-related increases in apoE mRNA in the order apoE4 > apoE3 > apoE2 and in apoE secretion in the order apoE4 > apoE2 > apoE3. Moreover, only the medium of apoE3 producing macrophages contained a particle with the mobility of γ-LpE. Whether these genotype-related differences in synthesis, secretion, and formation of apoE-containing particles by human macrophages cause differences in cholesterol efflux from macrophages is currently under investigation.