A lot of natural products are billing themselves as immune system boosters these days, but few of them are really backed by both longstanding use and science, as this one is. Some competing product can even backfire -- indiscriminately stimulating immune response as a whole. This may work in the short term to fend off an actual attack of a cold or flu, but can also increase your allergic responses to harmless things and wear you out, in the long term.
The Proligna in ImmunExtra is a patented extract of Scotch pine cones, whose medicinal benefits were recognized by the ancient Greeks and contemporary Japanese, and have been the subjects of intense research, which has found that not only can it reduce the levels of IgE (the immune molecule associated with triggering an allergic response) among those with allergies, but it can also dramatically increase the production of mature dendritic immune cells -- the type which learns the difference between true pathogens versus harmless allergens or even the body's own cells, and which marshal the activities of the immune system's Th2 (allergy/asthma) and Th1 (specific disease fighting) responses, accordingly.
Allera Health Products markets this product using the names Immune Extra and ImmunExtra - NPN: 80056907.
Abe M, Okamoto K, Konno K, Sakagami H. "Induction of antiparasite activity by pine cone lignin-related substances." In Vivo, 1989; 3(6):359-62.
Bradley WG, Widen RH, Weiser AM, Powers JJ, Fountain LB, Punjwani P, Lofgren SM, Hadzic T, Klein R, Green WH, Tanaka A. "The novel differentiation of human blood mononuclear cells into CD1a-negative dendritic cells is stimulated in the absence of exogenous cytokines by an extract prepared from pinecones." International Immunopharmacology 2003 Feb; 3(2):209-23.