We have shown that both xenografts and allografts of rat skin can be acutely and severely damaged by antisera specifically reactive with graft antigens, and that in appropriate circumstances the phenomenon can be elicited routinely (1, 2). A matter of paramount importance among the variables that influence the occurrence of this form of immunologically mediated tissue damage is the interval of time between the placement of the grafts and the administration of antiserum (3). Contrary to widely held views on the special vulnerability of grafts that are healing into place, it has been found that antiserum injected at the time of grafting or within 5-6 d thereafter has little detectable influence on the course or time of survival of the transplanted skin. This period of insusceptibility is rapidly succeeded by a state of sensitivity to humoral antibody that, in immunosuppressed hosts, reaches a peak of intensity at about 14-16 d after grafting and persists at decreasing levels for an additional 3 wk. Grafts that survive beyond that period of time regain their resistance to antiserum, and this state is maintained for the duration of survival of the grafts.We have analyzed these changes in the responses of xenografts of skin to antisera, and we have found that the initial state of insensitivity differs substantively from that observed in long-standing grafts. We describe here the results of our studies on freshly placed grafts, and in a succeeding paper (4) we report on the mechanisms involved in the acquired resistance of grafts that have survived for relatively long periods of time. Materials and MethodsAnimals. B6AF1 and CAFa mice were purchased from The Jackson Laboratory, Bar Harbor, Maine. Lewis (LE) and (Le × BN)F1 hybrid rats (LBN) were obtained from Microbiological Associates, Walkersville, Md. CD rats were purchased from the Charles River Breeding Laboratories, Wilmington, Mass.Antisera. Rabbit anti-mouse thymocyte serum (RAMTS) 1 was prepared as described (5) or was obtained from Microbiological Associates. 13 pools of antisera were used, the least potent of which extended the mean survival time of rat skin grafts to 32.5 :t: ! 1 d. Rabbit anti-rat *

Antibody-coated erythrocytes are lysed by murine C5- whole blood but not by plasma separated from such blood. The lytic activity has been shown to derive from platelets that attach to sensitized cells probably through membrane receptors for C3b. Whole blood or platelet-rich plasma (prp) obtained from mice that have been treated with purified cobra venom factor has little or no activity unless it is fortified with fresh C5- plasma. Lysis is observed only if the reactants are incubated at 37 degrees C and mechanical shaking is practiced, at least intermittently, throughout the period of incubation. Adherence of platelets and subsequent lysis are mediated by antibodies of a variety of immunoglobulin classes, including those that fail to mediate complement-dependent lysis. Platelet-mediated lysis is limited to cells to which the platelets adhere; 51Cr labeled, unsensitized cells that are mixed with prp and sensitized, unlabeled cells do not release 51Cr. Normal murine lymphoid cells and ascites tumor cells of mice, rats, and guinea pigs were apparently unaffected by sensitization and incubation with prp. However, because adherence of platelets to these sensitized cells was not observed, it is not clear whether the cells are resistant to the lytic action of platelets or whether the conditions of incubation were unfavorable for the attachment of platelets to the surfaces of nucleated cells. The significance of the lytic reaction described here is not known but may lie in antibody mediated release of microbicidal substances from platelets.

Laparoscopic pericardiotomy, biopsy, and external drainage can be performed effectively in a safe and efficient manner for benign and malignant pericardial effusions. This technique, although minimally morbid, allows for pericardiotomy with biopsy and placement of large drains under visual control. In this article, we describe the surgical technique, including external drain placement. We discuss our experience with laparoscopic drainage of an infected benign effusion with tamponade in a patient with chronic renal failure. A diagnostic laparoscopic pericardiotomy in a patient with penetrating lower thoracic trauma is also described. Potential advantages and disadvantages of the laparoscopic approach are discussed.

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