The causative agent of Jorge Lobo's disease, the fungus P. loboi (= Loboa loboi) may be seen extracellullarly tightly encircled by histiocytes: observations at the transmission and scanning electron microscopes

CORRESPONDENCE

The causative agent of Jorge Lobo's disease, the fungus P. loboi (= Loboa loboi) may be seen extracellullarly tightly encircled by histiocytes. Observations at the transmission and scanning electron microscopes

Lesioned skin tissues of patients with Jorge Lobo's disease (also known as lobomycosis) exhibit granulomata formed by closely adjoined histiocytes and some multinucleate, giant cells. Both the histiocytes and the giant cells contain intracytoplasmatic forms of the causative agent of the disease, the fungus P. loboi (=Loboa loboi) (ref. in BARUZZI et al., 1982¹; LACAZ et al., 1986² and SESSO & BARUZZI, 1988³). In the previous light microscopical studies, the parasites were consistently seen inside phagocytic cells. However, electron microscopical observations showed that restricted sectors of the outer region of the thickened cell wall of the fungus are in direct contact with the extracellular matrix either through exocytic-like openings or microchannel-like spaces delimited on both sides by host cell cytoplasm(s) (SESSO & BARUZZI, 1988³ and SESSO et al., 1988⁴), It was not possible to decide whether these cytoplasmic portions bordering the putative microchannel belonged or not to the same histiocytic cell. Should this last possibility prevail, then the parasite would be situated extra-cellularly (SESSO & BARUZZI, 1988³ and SESSO et al., 1988⁴) and the space resembling a microchannel would actually be the intercellular space between two histiocytes that tightly encircle the fungus.

In this report we show in sections and under the scanning election microscope that the fungus may be found extracellularly tightly shrouded by histiocytes.

Skin fragments from a Caiabi adult male Indian with lobomycosis were processed for observations under the transmission and the scanning electron microscopes. Ultrathin sections were obtained as indicated previouly (SESSO & BARUZZI, 1988³). For examination with the scanning electron microscope (SEM) processing was carried out according to the protocol of TANAKA & MITSUSHIMA (1983)⁵. In this procedure, after fixation in aldehydes the organ fragment before being exposed to osmium tetroxide is cracked at liquid nitrogen (-196ºC) temperature. When the cytoplasm of parasited cells is sectioned by the freeze-fracture procedure the intracellular form of the fungus is exposed for eventual observation with the SEM (Fig. 1).

The SEM used was the Stereoscan 240 (Cambridge) operated at 15 KV. Fig. 2 shows an empty cell wall of the fungus, encircled by the profiles of at least 3 histiocytes. Fig. 3 reveals that the parasitic form marked by C is encircled by 3 different histiocytes. The cell membranes of these histiocytes adhere to the irregularities of the outer surface of the parasite cell wall leaving no free extracellular space at the surface of the fungus.

It is as yet undetermined how frequently this type of interaction between fungus and histiocytic cells occurs in the granulomata of lobomycosis. To the extent of our knowledge, this arrangement through which phagocytic cells literally isolate (and apparently attempt to immobilize) a foreign parasitic element by the mechanical use of the cell bodies has no parallel in the literature.

One can not rule out the possibility that these histiocytes encircling the fungus will eventually fuse to form a multinucleated giant cell.

Laboratório de Patologia Molecular
Depto. de Patologia/FMUSP
Av. Dr. Arnaldo, 455
01246-903 São Paulo/SP
Brasil
Fone(011)853-6011 r.242/324/420
Fax:[phone]. Antonio SESSO
Flávio Paulo de FARIA Depto. de Medicina Preventiva
Escola Paulista de Medicina
Rua Botucatu, 740
04023-062 São Paulo/SP
Brasil. Roberto G. BARUZZI

REFERENCES

1. BARUZZI, R.C.; MARCOPITO, L.F.; VICENT, L,S. & MICHALANY, N.S. -Jorge Lobo's disease (keloidal blastomycosis) and tinea imbricata in indians from the Xingu National Park, Central Brazil. Trop. Doct., 12: 13-15, 1982.

2. LACAZ, C.S.; BARUZZI. R.G. & ROSA, M.C.B. - Doença de Jorge Lobo. São Paulo. Edição dos autores, Editora da Universidade de São Paulo, IPSIS Gráfica e Editora, 1986.

3. SESSO, A. & BARUZZI, R.G. - Interaction between macrophage and parasite cells in lobomycosis. The thickened cell wall of Paracoccidioides loboi exhibits apertures to the extracellular milieu. J. Submicrosc. Cytol. Path., 20: 537-548, 1988.

4. SESSO, A.; AZEVEDO, R.A. & BARUZZI, R.C. - Lanthanum nitrate labelling of the outer cell wall surface of phagocytized Paracoccidioides loboi in human lobomycosis. J. Submicrosc. Cytol. Path., 20: 769-772, 1988.

5. TANAKA, K. & MITSUSHIMA, A. - A preparation method for observing intracellular structures by scanning electron microscopy. J. Microsc., 133: 213-222, 1083.

Recebido para publicação em 18/02/1993

Aceito para publicação cm 26/02/1993

Publication Dates

• Publication in this collection
  20 July 2006
• Date of issue
  June 1993