[In vitro immunosuppressive effect of low density lipoproteins]

Immune cells participate in the formation of atheromatous plate, however little is known about the effects of native or oxidatively modified lipoproteins on these cells.

To study the effects of lipoproteins on in vitro mononuclear cell proliferation.

Peripheral blood mononuclear cells were obtained from 10 patients with type 2 diabetes mellitus (aged 52 +/- 9 years old with a disease duration of 8.2 +/- 5.7 years and a mean glycosilated hemoglobin of 9.3 +/- 2.2%) and 10 non diabetic healthy controls (aged 50.3 +/- 7.1 years old). These were stimulated with phytohemagglutinin (PHA) alone or in the presence of native LDLS, malondialdehyde modified LDLs or glycated LDLs. Proliferation was measured as 3H-thymidine incorporation and expressed as Stimulation Index (SI).

SI of patients and healthy subjects, after PHA stimulation were similar: (57.5 +/- 29.8 and 61.1 +/- 23.5) respectively LDLs did not induce proliferation in neither group. Native LDLs produced a 98% inhibition of PHA induced proliferation. Malondialdehyde modified and glycated LDLs caused a 50% inhibition. The suppressive effect was maintained when lipoproteins were incorporated to culture media 60 min prior or after PHA stimulation.

Lipoproteins inhibit in vitro PHA induced peripheral blood mononuclear cell proliferation both in diabetic and in non diabetic subjects.