[The mechanism of blood cell sedimentation. XIV. The effect of lysolecithin and nonesterified fatty acids on the blood cell sedimentation rate]

Role of serum in inhibition of cultured lymphocytes by lysophosphatidylcholine

Serum was heated at various temperatures to inactivate components which might be involved in the regulation of lysophosphatidylcholine (lysoPC) levels in rabbit lymph-node cell cultures. Cells cultured in medium containing serum preheated for 20 min at 66 degrees C ("66 degrees C-serum") were inhibited much more by exogenous lysoPC (5 microM) than were cells cultured in medium containing control serum ("38 degrees C-serum"). This was observed over a 20 h culture period as a slow increase in inhibition of cell labelling with [3H] uridine, which reflected cytotoxic cell damage. Heating serum at 66 degrees C caused (i) conversion of monomeric albumin to highly polymeric forms which were deficient in lysoPC-binding activity, (ii) transfer of lysoPC from albumin to lipoproteins, predominantly high density lipoproteins, and (iii) inhibition of two lysoPC metabolizing activities (which were detected only at low levels in control serum). Addition of albumin to cultures containing 66 degrees C-serum decreased the toxicity of lysoPC to the same extent as did the addition of control serum with an equivalent albumin content. Thus, albumin was the major heat-labile factor protecting cells against lysoPC. However, cell inhibition by lysoPC was dependent on the sequence of heating serum and lysoPC addition. Inhibition was small when lysoPC was added before heating the serum. This could not be explained by a detectable difference in the binding of lysoPC to serum components. Furthermore, although radioactive labelling of cells with [14C] lysoPC was increased in 66 degrees C-serum, this did not correlate with cell inhibition. Increased labelling with [14C] lysoPC occurred several hours before significant cell inhibition was evident and was not affected by the sequence of heating and lysoPC addition. Since preincubation of lysoPC with 66 degrees C-serum increased the inhibition, it is suggested that the heated serum lysoPC generates another factor which is responsible for the cytotoxic effects observed.

[Diagnostic significance of heat-induced inhibition of erythrocyte sedimentation (author's transl)]

Heat-induced inhibition of erythrocyte sedimentation (HIES) was examined in 158 cases. HIES is significantly lower in patients with a liver cell damage isolated or due to metastases of a neoplastic process in comparison to that in patients suffering from inflammation or malign tumor not involving the liver. Generally, HIES depends upon the concentration of lysophosphatidyl choline (lysolecithin) which is set free in plasma by lecithin-cholesterol-acyltransferase (LCAT) during incubation. In patients with lever cell damage, LCAT is diminished. HIES is being influenced by several factors: Lysophosphatidyl choline is bound to albumin, and this prevents its reaction on the erythrocyte surface. Lysophospholipase reduces the concentration of lysophosphatidyl choline in the plasma by splitting off its fatty acid in the alpha-position. Specific serum proteins, the so-called agglomerines, which are responsible for the acceleration of erythrocyte sedimentation, are counteracting the HIES. The concentration of albumin and agglomerines in plasma and the activity of lysophospholipase are subject to physiologically and pathologically caused deviations. Thereby, HIES is being influenced individually at varying degrees. This makes it difficult to estimate the LCAT activity which represents the principal cause of HIES. As a consequence, HIES seems not to be suitable for clinical diagnostics.

The significance of plasma lipoproteins on erythrocyte aggregation and sedimentation

Increased erythrocyte aggregation can be induced by high concentrations of human lipoproteins. The dependence of aggregate formation on lipoprotein concentration was recorded by determination of erythrocyte sedimentation rate (ESR), by electrical measurement of the erythrocyte aggregation index (EAI) and by scanning electron microscopy. The lipoprotein concentrations necessary to induce a significantly increased ESR in an otherwise normal human plasma are much too high to be encountered in physiologic or even severe pathologic states. Therefore hyperlipoproteinaemia by itself cannot explain a raised ESR. In cases where the ESR is raised due to the presence of increased amounts of other erythrocyte aggregating plasma proteins (agglomerins), hyperlipoproteinaemia can contribute to a limited extent to the increase in ESR. The possible pathophysiological significance of the demonstrated erythrocyte aggregating capacity of human lipoproteins in a microvascular environment is noted.