From a summary:

Drinking damages the liver and may make the body more vulnerable to infectious diseases, including sexually transmitted infections and tuberculosis.

Or from the review itself:

Infectious disease

The causal impact of alcohol on the four broad categories of infectious disease from the last Global Status Report on Alcohol and Health [1] has been confirmed in recent reviews [15, 16]. The main biological mechanism involves alcohol-induced liver dysfunction, which disrupts both non-specific innate and adaptive immune responses through acute and chronic alcohol consumption [80-84]. Lowered immune responses increase susceptibility to communicable diseases. More specific biological pathways are described in the references listed in Table 1.