HUMORAL IMMUNOSTIMULATION .7. SIALIC-ACID MASKS ANTIGENIC SITES ON AN ANTIBODY-SELECTED VARIANT CELL LINE

  • 1 January 1977
    • journal article
    • research article
    • Vol. 119  (2) , 614-617
Abstract
Variant cell lines (LC1, LC2) obtained by growth of mouse [fibroblast] L cells (L) in cytostimulatory and cytotoxic doses, respectively, of rabbit anti-L cell antiserum (AL) are altered in many ways relative to the parent cell line. A major change is the reduction of those surface membrane antigens that AL recognizes. These cell variants are now found to have increased membrane sialic acid relative to L. Treatment of intact variant cells with neuraminidase (50 units/ml, 37.degree. C, 1 h) greatly restored the susceptibility to LC1 to lysis with AL. In the presence of 1/100 dilution of AL and 5% complement the viability indices (1.00 = no cell kill) of untreated and neuraminidase-treated cells were, respectively: L 0.10 and 0.03 and LC1 0.91 and 0.40. Neuraminidase-treated LC2 cells retained their resistance to AL. Parallel studies with 125I-ALIg[immunoglobulin]G showed increased binding to neuraminidase-treated LC1 relative to native LC1. Apparently the altered membrane sialic acid content affects the immunologic behavior of this cell variant by masking the original cell surface antibody-binding sites. This represents a possible mechanism for tumors to escape immunologic control.

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