Human T-lymphocyte activation : interactions between lymphocytes and mitogenic or non-mitogenic lectins

• The aim of this investigation was to gain further insights in the mechanisms of T-lymphocyte activation by lectins. Interactions between the lectins and purified lymphocytes from human peripheral blood, were studied in the following respects: in vitro culture requirements for lectin induced DNA-synthesis, intercellular regulations of the mitogen response and binding of lectins to lymphocyte surface components. The results can be summarized as follows: 1) Transferrin (>10 pg/ml) can fully substitute for serum or albumin as growth promotor in cultures of lectin stimulated T-cells. 2) The T-lymphocytes from the blood comprise at least three functionally different subpopulations. One subpopulation is highly responsive to mitogen stimulation (leucoagglutinin. La) regardless of the method used for T-cell purification. A second subset responds only marginally but shows elevated (/h)-thymidine incorporation upon mitogen stimulation if the cells were first subjected to resetting with sheep erythrocytes. The response of the latter population is suppressed by a third T-cell subset, characterized by Fc-receptors for IgG. 3) The mitogenic capacity of a lectin is not exclusively determined by its multivalence or the strength of its interaction with membrane receptors. 4) There is no marked difference between mitogenic and non-mitogenic lectins in the number of lectin molecules bound per lymphocyte. 5) There are surface structures on the T-cells which are recognized by mitogenic lectins but not by a non-mitogenic lectin. 6) Mitogenic lectins bind a significantly larger number of surface glycopeptides in T-cell lysates than the non-mitogenic lectins. Five glycopeptides are selectively bound by mitogenic lectins but not by non-mitogenic lectins. It remains to be established if the surface components selectively bound by mitogenic lectins are present on the T-cells which are stimulated and if it is the interaction of the lectins with one or several of these glycopeptides which triggers mitogenicity.

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MEDICIN OCH HÄLSOVETENSKAP  -- Medicinska och farmaceutiska grundvetenskaper (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Basic Medicine (hsv//eng)

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