A ground‐based model to study the effects of weightlessness on lymphocytes

Abstract

The mitogenic response of human lymphocytes was found to be markedly reduced in weightlessness conditions as compared to normal gravity. One possible explanation is that due to the non-existent sedimentation in space the lymphocytes could not adhere and spread on a substratum. Thus, we investigated the effect of substratum adhesiveness on lymphocyte responsiveness by reducing and blocking cell adhesion with poly-HEMA in a simple on-ground system. Lymphocyte adhesiveness was assessed by measuring the proportion of non-adhesive, slightly, and strongly adhesive 51Cr-radiolabelled cells on uncoated and poly-HEMA coated plastic. The amount of cell spreading on surfaces with varying adhesiveness was determined by measuring the area of cells. Cells grown on medium and thick poly-HEMA films were rounded in shape. By contrast, on tissue culture plastic, they showed clear signs of spreading. The mitogenic response of lymphocytes grown on thick poly-HEMA films was reduced by up to 68% of the control (tissue culture plastic). Interferon-gamma production was virtually nil when the cells were grown on the least adhesive substratum. These results show that activated lymphocytes need to anchor and spread prior to achieving an optimal proliferation response. We conclude that decreased lymphocyte adhesion could contribute to the depressed in vitro lymphocyte responsiveness found in the microgravity conditions of space flight.

Suppressed PHA activation of T lymphocytes in simulated microgravity is restored by direct activation of protein kinase C

“…However, when we tried to increase the amount of cell-cell contact by increasing cell densities in the RWV, proliferation was not restored. Although some studies suggest that cell-substratum interaction is important to T cell activation [59], we found that PBMC activated with PHA in Teflon culture bags was unaffected. The ability of cells to interact with substratum may not be as important as the ability to interact with other cells.…”

The kinetics of translocation and cellular quantity of protein kinase C in human leukocytes are modified during spaceflight

“…Likewise, under 1-g conditions, nonadherent cells of the type used in our experiments sediment to the floor of the culture container, which increases the possibility of cell to cell contact and mechanical interaction with the culture vessel, compared with cells in suspension, as would be the case for cells under microgravity. Although the cell types used in our experiments proliferate in an anchorage-independent manner, complete inhibition of attachment to the cell culture vessel has been reported to inhibit proliferation (32). In contrast, it is much less obvious how change in gravity could be directly perceived by a single cell.…”

T cell activation responses are differentially regulated during clinorotation and in spaceflight

“…The clinostat model system (clinorotation) is a ground‐based method for providing a vector‐averaged reduction in the apparent gravity on the cell culture (4, 5). Clinorotation of samples was performed at 37°C in 1.2 ml cryovials (Corning Glass Works, Corning N.Y.) filled to capacity.…”