A limiting dilution assay for the quantification of Leishmania major in infected mouse tissue was developed. The assay was found to be both sensitive and reliable, and, due to its design, could be scored either visually or following the incorporation of 3H-thymidine by the growing parasites. Results are presented in which the assay was employed to enumerate L. major in the tissues of susceptible (BALB/c) and resistant (CBA) mice at intervals after infection with L. major. It was found that parasites could be detected at the site of injection with L. major as early as 3 days after infection. By day 8, a substantial increase in the number of parasites at the lesion site had occurred in both strains of mice. Subsequently, whereas the number of parasites decreased in the lesions of CBA mice, their number steadily increased in the lesions of BALB/c mice. Parasites were detected in lymph nodes draining the lesion site in both BALB/c and CBA mice by 28 days after infection. Interestingly, a low number of L. major was found in the lymph nodes of CBA mice at 100 days after infection, a time when no parasites could be detected at the lesion site. Previous results from this laboratory have demonstrated that the adoptive transfer of L. major-specific L3T4-positive T-cell populations exacerbated cutaneous lesions induced by L. major in BALB/c mice. Experiments presented here indicate that the adoptive transfer of L. major-specific T-cells also exacerbated cutaneous leishmaniasis in CBA mice. Using the sensitive limiting dilution assay presently described, it was found that this unexpected exacerbative effect of L. major-specific T-cells on lesion development was accompanied by a substantial increase in the number of parasites in the lesions of the adoptively transferred mice.

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Human gene MAGE-I codes for an antigen that is recognized on melanoma cells by autologous cytolytic T lymphocytes (CTL). This antigen is potentially useful as a target for cancer immunotherapy because gene MAGE-I is not expressed in any normal tissues except the testis. We tested 46 surgical samples of non-small-cell lung carcinomas and observed MAGE-I expression in 16 of them (35%). Genes MAGE-2 and 3, which are closely related to MAGE-I, were expressed by a similar proportion of these tumors. Some small-cell lung tumors also express MAGE genes. The proportion of tumors expressing MAGE-I suggests that lung tumor patients may constitute the largest group of patients potentially eligible for pilot studies involving MAGE-I immunization.

This paper examines the properties of the optimal nonlinear income tax when preferences are quasi-linear in leisure and individuals differ in their ability and their preferences for leisure. The government seeks to redistribute income. It can perfectly observe the level of endogenous income but cannot observe either ability or preferences. The heterogeneity of preferences leads to problems of comparability between individual utilities which challenge the design of redistributive schemes. We analyze the consequences of adopting a utilitarian social welfare function where the government is allowed to give different weights to individuals with different preferences. Under this particular social objective and given the quasi-linearity of preferences, we are able to obtain closed-form solutions for the marginal tax rates and to examine the progressivity of the tax system according to the weights used. Copyright Blackwell Publishing, Inc. 2002.

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Tax and expenditure policies are studied in a federation with imperfectly mobile households. States implement a linear progressive tax and supply a public good. A vertical scal externality, re ecting the e ect of state policies on federal revenues, provides an incentive for state taxes to be too progressive. A horizontal scal externality causes non-optimal states taxes and expenditures because of the migration e ect. The federal government implements its own linear progressive tax and makes transfers to the states. The federal government can nullify both externalities by appropriate scal policies, and redistributive taxation can be decentralized to the states.