Innate and Acquired Immunity in Cryptococcus neoformans Infections of the Central Nervous System

Chapter · December 2004with38 Reads
DOI: 10.1007/0-387-25445-5_24


    Cryptococcus neoformans is an encapsulated yeast that causes cryptococcosis, a life-threatening disease that develops following inhalation and dissemination
    of the ubiquitous organisms. C. neoformans has a predilection for the CNS, and mortality is most frequently associated with meningoencephalitis. Individuals with deficiencies
    in cell-mediated immunity, such as AIDS patients, are more susceptible to cryptococcosis; thus, the incidence of cryptococcosis
    is increasing as a result of the growing number of immunocompromised individuals. Loss of CD4+ T cells predisposes individuals to progressive infection with C. neoformans, further emphasizing the importance of cell-mediated immunity in host resistance to this organism and partially explaining
    the high incidence of cryptococcosis in AIDS patients. Although much has been learned about host defense mechanisms against
    C. neoformans in the lungs, less is known about host resistance in the CNS. Clearly, some of the same cells and mechanisms are involved
    in host defense in the lungs and the CNS; however, the CNS has unique features that suggest there might be some differences
    as well. In fact, experimental evidence indicates that many anticryptococcal reactions in the CNS are delayed in comparison
    to extracerebral tissues, which may be due to differences in immune mechanisms in the CNS compared to other tissues. More
    defined experimental studies are required to identify the critical components needed for appropriate anticryptococcal activity
    in the CNS that restricts growth of C. neoformans while at the same time does not cause harmful damage to the nervous tissue.