Enter the "Role of sugars in human neutrophil phagocytosis". This paper was published in 1973 in the American Journal of Clinical Nutrition. Volunteer subjects were dosed with 100 grams of carbohydrate following a 12-hour fast (basically not eating overnight), then blood samples were taken at intervals afterwards and examined. While a number of blood conditions did not change, most notably the number of white blood cells present in the samples, there was one interesting change. Here's a sentence from the abstract giving you the result:
"Oral 100-g portions of carbohydrate from glucose, fructose, sucrose, honey, or orange juice all significantly decreased the capacity of neutrophils to engulf bacteria as measured by the slide technique." Also, "The greatest effects occurred 1 and 2 hr postprandial, but the values were still significantly below the fasting control values 5 hr after feeding."
Blood sugar has an effect on your immune system? This is not news for diabetics, but these volunteers were all healthy individuals. Now, this was a small sample size (about 10 people), being fed carbohydrates in an isolated form, and with the exception of honey or orange juice, presumably a form not to be found in nature. As with a number of nutritional studies, these factors must be taken into account when interpreting the results in a real-world setting. However, I find these results very interesting.