Seven commercially available sunscreens were compared by three different methods. Absorbance spectra were measured for each product in isopropanol solution and also on hairless mouse epidermis. In uiuo tests were performed on human volunteers using a Xe arc solar simulator. Sun Protection Factors (SPF) were calculated by each method for each product tested and the results compared. By all methods used, the combination of 7% octyl dimethyl para-aminobenzoic acid and 3% oxybenzone provided the most protection from U.V. light. While estimates of the effectiveness of all products were much too high when calculated by the isopropanol solution method, the hairless mouse epidermis technique seems to be an accurate tool for predicting product efficacy in uiuo.

Increasing UVB radiation at the earth's surface might have adverse effects on in vivo immunologic responses in humans. We prospectively randomized subjects to test whether epicutaneous immunization is altered by prior administration of biologically equalized doses of UV radiation. Multiple doses of antigens on upper inner arm skin (UV protected) were used to elicit contact sensitivity responses, which were quantitated by measuring increases in skin thickness. If a dose of UVB sufficient to induce redness (erythemagenic) was administered to the immunization site prior to sensitization with dinitrochlorobenzene (DNCB), we noted a marked reduction in the degree of sensitization (P < 0.0006) that was highly dose responsive (r = 0.98). Even suberythemagenic UV (less than a visible sunburn) resulted in a decreased frequency of strongly positive responses (32%) as compared to controls (73%) (P = 0.019). The rate of immunologic tolerance to DNCB (active suppression of a subsequent repeat immunization) in the groups that were initially sensitized on skin receiving erythemagenic doses of UV was 31% (P = 0.0003). In addition, a localized moderate sunburn appeared to modulate immunization with diphenylcyclopropenone through a distant, unirradiated site (41% weak responses) as compared to the control group (9%) (P = 0.05). Monitoring antigen presenting cell content in the epidermis revealed that erythemagenic regimens induced CDla-DR+ macrophages and depleted Lrhans cells. In conclusion, relevant and even subcinical levels of UV exposure have significant down modulatory effects on the ability of humans to generate a T-celi-mediated response to antigens introduced through irradiated skin.

The risks incurred from increased exposure to UVA II (320-340 nm) (i.e. during sunscreen use and extended outdoor exposure, tanning parlors) are not well understood. Therefore, we explored the effects of UVA II on skin immune responses in humans. After a single local exposure (4 minimum erythemal dose [MED]) using a xenon are lamp filtered with a narrow bandpass filter (335 +/- 5 nm full width at half maximum), individuals were contact-sensitized with dinitrochlorobenzene (DNCB) through a UVA II exposure site or through normal skin. UVA II induced a marked decrease in the magnitude of skin immune responses (P < 0.0001). The UVA II group had only 29% successful sensitizations, as compared to 83% in the control group. The percentage of individuals who remained tolerant to DNCB after two sensitizations was 23.6% for the UVA II-exposed group, as compared to 3.8% in the controls (P = 0.006). UVA II also uniquely altered the type of antigen-presenting cells present in the epidermis. Human leukocyte antigen (HLA)-DR+ cells in control epidermal cell suspensions (C-EC) comprised a single, homogeneous population of Langerhans cells (LC) with the phenotype: CD1ahi DRmid CD11b CD36 (1.5 +/- 0.3% of EC). UVA II irradiation reduced the number of such LC to 0.6 +/- 0.2% of EC. Although cells expressing the macrophage phenotype: CD1a- DRhi CD11b+ CD36+ were increased in UVA II skin, relative to C-EC, these comprised only 10.1 +/- 6.1% of the DR+ cells, which is less than that after UVB exposure. Also distinct from UVB, a third population was found in UVA II-EC, which exhibited a novel phenotype: CD1a+ DR+ CD36+ CD11b+; these comprised 11.1 +/- 6.9% of the DR+ UVA II-EC. In conclusion, despite the above differences in infiltrating DR+ cells, both UVB and UVA II reduce the skin's ability to support contact sensitization, induce active suppression (tolerance) and induce a reduction in LC.

The polymorphism of Mycobacterium tuberculosis strains was evaluated in French Polynesia, an area with a low incidence of tuberculosis and a population which has been geographically stable during recent decades. Nonrepetitive strains isolated from 64 patients during 1991 and 1992 were subjected to DNA restriction fragment length polymorphism (RFLP) analysis, using the insertion sequence IS6110 and the repetitive element DR as probes. Thirty-eight different IS6110 RFLP types were identified. They could be clustered in 11 groups. All the members of each group are identical or differ by one to three bands. All the other strains are gathered in the miscellaneous group. In some cases, transmission of strains with identical RFLP types between patients of the same family or between patients living in the same area was identified. Strains exhibiting similar IS6110 RFLP types also exhibited identical DR RFLP patterns, confirming that strains with similar types were genetically linked. Strains belonging to two different IS6110 clusters exhibited the same DR RFLP type. These data may also indicate a common origin for these strains and evolution to new IS6110 types. The results obtained in this study suggest that not only reactivation of latent tuberculous infections but also active transmissions are still occurring in French Polynesia.

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