The invention provides a modified citrus pectin (MCP) for use in a method of enhancing the activation of T-cytotoxic suppressor lymphocytes by a mammal in response to an immune challenge, comprising administering to said mammal an amount of MCP effective to increase T-cytotoxic suppressor lymphocyte activation by said mammal, as compared with the level of activation by said mammal in the absence of administration of said MCP.
