- Alcoholism is known to compromise the immune system.
- African-American alcoholics are at greater risk for certain infectious diseases.
- African-American ethnicity, in conjunction with alcoholism, seems to signify a more compromised immune system.
- These immune changes may be the link to a greater risk for infectious diseases.
"We know from epidemiological data that African-American alcoholics are at greater risk for certain infectious diseases such as tuberculosis, hepatitis C and HIV," said Michael Irwin, professor of psychiatry at San Diego Veterans Affairs Medical Center and the University of California, San Diego, and lead author of the study. One study found, for example, that among veterans with alcoholic liver disease, African Americans were 2.4 times more likely to have hepatitis C. "African-American alcoholics also have increased mortality rates," he added.
The study examined the effects of chronic alcoholism on three aspects of the immune system. The first was to measure the activity level of "natural killer cells," a sort of first-line defense of cells in the body that kill other cells already infected by an invading virus. The second was to test the response level of natural killer cells that were artificially stimulated. The third was to look at the production of two types of hormone-like proteins called cytokines that regulate the intensity and duration of immune responses. Interleukin-6 (IL-6) is an inflammatory cytokine that essentially turns on the immune system. Interluekin-10 (IL-10) is an inhibitory cytokine that essentially turns off the immune system.
The findings indicated an across-the-board decrease in natural killer cell activity among all of the alcoholics, but the decrease was more pronounced in the African Americans. African-American alcoholics also showed the greatest decline in natural-killer cell activity following artificial stimulation. Furthermore, the expression of IL-6 (the 'on' signal) was lower while the expression of IL-10 (the 'off' signal) was higher among African-American alcoholics; Irwin called this finding a "double whammy. Not only do they have less production of signals that activate the immune system, but they also more signals that turn off the immune system." In summary, he noted, alcoholics have a compromised immune system, African-American alcoholics show the greatest immune changes, and this may explain why African-American alcoholics are at greater risk for infectious diseases.
"Showing that ethnic background makes a difference in terms of immune changes is a very important finding," said Steven J. Schleifer, chair of the Department of Psychiatry at the University of Medicine and Dentistry of New Jersey - New Jersey Medical School. "There are increasing suggestions that many biological functions differ among ethnic groups, by gender, by age, and so on. Depending on your demographic background, your baseline biological function in some areas like the immune system could be altered." In other words, he explained, two healthy people with different biological constitutions could respond to something that's toxic to the immune system -- like alcohol -- in different ways.
"You may need the two risk factors, so to speak," Schleifer explained, "to see any results. Neither one alone -- alcohol itself or being African American -- may have much of an effect. But if you have both elements, constitutional factors may make you more susceptible."
Schleifer noted that too often studies will look at the outcome and consequences of alcoholism while not systematically controlling for influencing factors. "Many of these research studies," he said, "don't tend to carefully distinguish men from women, younger people from older people, people by ethnic differences, whether people have other medical problems or not, or whether they have concurrent use of substances other than alcohol." He added that "Dr. Irwin has shown that you can't ignore those factors, that something which could be benign in one group of individuals could be very toxic in another group."
Irwin's other research has examined the potential influence of depression, stress levels, and disordered sleep on the immune system. He observed that some of the mechanisms which connect these atypical conditions to immune alterations may be very similar in nature.
Schleifer offered suggestions for future research. "First of all, we need to really nail down what it is about the ethnic group that is putting them at risk. Could it be nutrition, socio-economic status, general effects of poverty? Then we need to show that those people showing the most dramatic immune changes in laboratories are, in fact, those people at greatest risk of developing health problems in the real world. Ultimately, what we want to be able to do is not simply make general conclusions, but be able to identify particular individuals at greatest risk so that we can intervene."
The co-author of the Alcoholism: Clinical & Experimental Research paper was Claudine Miller of San Diego Veterans Affairs Healthcare System. The study was funded by the National Institutes of Health and the National Institute of Alcohol Abuse and Alcoholism.