Miller G P
University of Texas Medical School, Program in Infectious Diseases and Clinical Microbiology, Houston 77225.
Semin Respir Infect. 1986 Mar;1(1):45-52.
Cryptococcus neoformans is a ubiquitous fungus found in the soil. Upon inhalation, a complex, incompletely understood series of host responses begins that determines whether the infection will be controlled or will progress to local or disseminated disease. Local pulmonary disease may be asymptomatic or may pursue a subacute course with mild pulmonary symptoms and systemic complaints suggestive of tumor. In the compromised host, however, symptomatic pulmonary disease is often the harbinger of systemic dissemination. Early host responses include phagocytosis by polymorphonuclear leukocytes aided by complement activation which provides opsonins. Lymphocytes are activated to produce lymphokines which may enhance macrophage phagocytosis and intracellular killing of ingested cryptococci. Other lymphocytes may function as natural killer-like cells or inhibit the growth of the fungus. Production of antibody further facilitates phagocytosis by both polymorphonuclear leukocytes (PMN) and monocytes (MC). In the presence of antibody, both PMN and MC demonstrate antibody-dependent cell-mediated cytotoxicity. The combination of humoral and cell-mediated immunity in normal hosts appears to provide excellent protection against disseminated infection as evidence by the rarity of disease in exposed individuals with positive skin tests. By contrast, the frequency of cryptococcal disease in steroid-treated individuals, allograft recipients, and AIDS victims highlight the importance of T lymphocyte dependent host defenses. In view of compelling in vitro evidence for the importance of humoral responses, the infrequency of cryptococcal disease in patients with gammopathies remains a puzzle.
新型隐球菌是一种在土壤中普遍存在的真菌。吸入后，一系列复杂且尚未完全了解的宿主反应就会开始，这些反应决定了感染是会得到控制还是会发展为局部或播散性疾病。局部肺部疾病可能无症状，也可能呈亚急性病程，伴有轻微肺部症状和提示肿瘤的全身症状。然而，在免疫功能受损的宿主中，有症状的肺部疾病往往是全身播散的先兆。早期宿主反应包括多形核白细胞在补体激活产生调理素的辅助下进行吞噬作用。淋巴细胞被激活产生淋巴因子，这些淋巴因子可能增强巨噬细胞的吞噬作用以及对摄入的隐球菌的细胞内杀伤。其他淋巴细胞可能发挥自然杀伤样细胞的作用或抑制真菌生长。抗体的产生进一步促进了多形核白细胞（PMN）和单核细胞（MC）的吞噬作用。在有抗体存在的情况下，PMN和MC均表现出抗体依赖性细胞介导的细胞毒性。正常宿主中体液免疫和细胞介导免疫的结合似乎能为抵抗播散性感染提供良好的保护，这从皮肤试验呈阳性的暴露个体中疾病罕见可以得到证明。相比之下，接受类固醇治疗的个体、同种异体移植受者和艾滋病患者中隐球菌病的发生率凸显了T淋巴细胞依赖性宿主防御的重要性。鉴于有令人信服的体外证据表明体液反应很重要，免疫球蛋白病患者中隐球菌病发生率低仍然是一个谜。
