Seasonal conditions determine the manner of skin rejection in reptiles

Abstract

During summer, 33%,52%, and 15% of lizards Chalcides ocellatus rejected first set skin allografts (time between day of first sign of rejection and end point), respectively in an acute (11)(12)(13)(14) days), subacute (15-20 days), and chronic (21)(22)(23)(24) days) manner. Second set grafts were rejected in an acute fashion (8)(9)(10)(11)(12)(13) Several reports have documented that different reptilian species reject skin allotransplants in a typically chronic fashion (Maslin, '67; Manickavel and Muthukkaruppan, '69; Borysenko, '69, '70; Terebey, '72; Worley and Jurd, '79; Badir et al., '81). Suggestions have been made attributing this poor cell-mediated reactivity to the absence or low polymorphism of major histocompatibility complex (MHC) class 1/11 loci (Flaherty and Cohen, '82). However, Cuellar and Smart ('77, '79) have reported several instances of acute skin graft rejection in the lizard Cnemidophorus tigris. Also, studies from our laboratory have indicated that lizards and snakes possess a n advanced type of immune system and display the major immunologic functions related in mammals to the presence ofthe MHC, including acute skin graft rejection (Saad and El Ridi, '84; El Ridi et al., '88; Farag and El Ridi, '90). The present study was undertaken to provide detailed and significant information on the controversial issue of skin graft reactivity in reptiles. The data revealed that the lizard Chalcides ocellatus rejects skin graft acutely during the optimal summer season, and in a chronic manner during the rest of the year when the ambients conditions are generally unfavourable for expression of its full immune potential (El Ridi et al., '88). MATERIALS AND METHODSLizards Adult male and female scinks, Chalcides ocellatus (Reptilia, Sauria, Scincidae) weighing 10-25 g and of 7-15 cm (snout to vent) were collected from neighbouring gardens and fields during the four consecutive seasons. Lizards were maintained in cages containing 30 cm deep sand in an unconditioned animal room at 33-38°C in summer, 20-32°C in autumn and spring, and 10-17°C in winter, and given wood lice Porcellio laevis and tap water ad libitum. Grafting techniqueSkin grafts were exchanged between random lizard pairs, so that each individual received and donated one graft. Lizards were anesthetized by ether inhalation. Ventral and dorsal skin was sterilized by 70% ethyl alcohol, and about 8-10 mm2 of skin was excised from the ventral side of each lizard, cut into equal parts, and placed on cotton wetted with 70% alcohol for less than 5 min. Two graft beds were prepared on the dorsal side of each lizard and the ventral skin fragments were transplanted one onto the donor and the other on the partner, as auto-and allografts, respectively. The dorsal skin excised from each lizard was placed on its ventral side to prevent infection. Grafts were rotated 180" before insertion under the edges of the graft bed and consequently the graft scales were pointing forwards. The wounds on the dorsal and ventral sides of each lizard were sprinkled ...

Understanding the vertebrate immune system: insights from the reptilian perspective

“…Afifi et al found a seasonal pattern in the ability of the ocellated skink (Chalcides ocellatus) to reject skin grafts (Afifi et al, 1993). The timing of the onset of rejection was longest in the winter, with rejection delayed until the following spring.…”

Biology of stress: interactions with reproduction, immunology and intermediary metabolism

“…The functional role of granulocytes and monocytes in reptilian immune systems is almost unknown, although their presence suggests relative importance (Cooper et ai., 1985). Evidence for a major histocompatibility complex (MHC) in ectotherms is largely based upon functional studies such as allograft rejection (Afifi et al, 1993) and mixed leucocyte reaction (Saad et al, 1986). Reptiles synthesize at least two classes of immunoglobulin (Ig): a high molecular weight Ig related to mammalian IgM, and a more distantly related Ig, termed IgY, of lower molecular weight (EI Ridi, 1992).…”

Widespread seasonal gene expression reveals annual differences in human immunity and physiology

“…Periodic seasonal changes have influenced all life forms, as exemplified by seasonal physiology and behaviours across plant and animal species 1 2 3 . For example, reptile graft rejection 4 and level of gonadal hormones in squirrel monkeys 5 display seasonal variation. In humans, many complex polygenic diseases, including cardiovascular 6 7 , autoimmune 8 9 and psychiatric illnesses 10 11 12 , have established seasonal patterns of incidence and disease activity.…”