Optical transforms of epidermal Langerhans' cell granules.

The internal structure of the epidermal Langerhans' cell granule (LCG) was studied with optical transforms of electron micrographs representing 3 planes of sectioning. Its "limiting membrane" exhibited linear discontinuity with a periodicity of about 11 nm similar to the structural repeats of the core (10.8 mm) in both the "outer" and the "internal leaflets". The average thickness of the nonvesicular part of the LCG was 55.7 nm. Disarray present in the optical diffractograms was incompatible with crystallinic or paracrystallinic orderliness of the periodic structures in the LCG. The structure appeared as an assembly of 4 sheets of roughly hexagonally packed particles: The stacked particles of 2 sheets in orthogonal contact forming the core (13.2 nm) were separated by an intermediate space (2.7 nm) from the single sheet of the outer layer and staggered by one-half the particle diameter on cross-sections. The validity of this model was inferred from the similarity of optical transforms of model structures.