Haemolytic anaemia in the rabbit following the injection of human anti-I cold agglutinins

Anti-I cold agglutinins, purified from the serum of patients with chronic cold haemagglutinin disease, were injected intravenously into adult rabbits, which are known to have I antigen on their red cells. This caused acute intravascular haemolysis, with haemoglobinaemia, haemoglobinuria and anaemia. In addition, there was an acute, but usually transient, thrombocytopenia and neutropenia. Anticoagulation with heparin or Arvin had no influence on the effects of cold agglutinin injection, but massive doses of heparin, thought to interfere with complement binding by the cold agglutinin, did prevent the haemolysis, thrombocytopenia and neutropenia. A rabbit, given daily injections of cold agglutinin, developed significant intravascular haemolysis only with the first injection. However, a chronic extravascular haemolytic anaemia occurred with marked spherocytosis, reticulocytosis and shortening of the red cell survival. The effects of injection of human anti-I cold agglutinins into rabbits are analogous to certain aspects of the human disease and this rabbit model may be useful in further studies of in-vivo complement binding and removal of complement coated cells.

The nature of experimental second-set kidney transplant rejection. 3. The role of complement

Second-set kidney transplant reactions occur in decomplemented dogs. The microscopic features of the reaction under such conditions indicate that the typical acute inflammatory reaction has occurred. Since the factors (presumably antibodies) mediating the second-set reaction are not dependent on complement fixation it is unlikely that HL-A antibodies, which are dependent on complement fixation for cytotoxicity, can be implicated in so-called hyperacute rejection (i.e. second-set rejection) in humans. The microscopic features of a genuine second-set reaction in humans are identical to those originally described in the dog. Since the first observable sign of the second-set kidney reaction is vasoconstriction of the outer cortical vessels, it is essential to establish how a severe antigen-antibody reaction can evoke such a rapid destruction of a kidney allotransplanted to a previously sensitized recipient. It is glomerular basement membrane which first bears the brunt of the second-set reaction. Tubular damage appears to follow gross ischaemia resulting from afferent renal vasoconstriction. Since the antigens of renal basement membrane are not represented on the lymphocytes, serious problems arise in attempting to assess renal histocompatibility by lymphocyte markers.

The in vivo behaviour of complement-coated red cells: studies in C6-deficient, C3-depleted and normal rabbits

Two series of experiments were performed on rabbits to investigate the role of fixed C3 in the non-lytic destruction of red cells. In the first series, intravenous injection of a potentially lytic IgM cold antibody (anti-I) into C6-deficient rabbits caused a severe thrombocytopenia and neutropenia and a fall in haemoglobin concentration and PCV with only minimal haemoglobinaemia; all were of short duration. A sharp fall in plasma C3 concentration, the demonstration of C3 on the red cells and the occurrence of immune-adherence in vivo suggested that red cell-complement intermediates in the form EA_(IgM) C1423 were present in the circulation at this time. Subsequently, when the fixed-C3 activity of the circulating red cells was markedly diminishing, the haemoglobin and PCV and platelet and neutrophil counts recovered towards the pre-injection values, indicating the sequestration rather than the acute destruction of these cells. In contrast to the findings in the C6-deficient rabbits, injection of the same IgM cold antibody into C3-depleted rabbits caused no significant haematological changes. In a second series of experiments, red cells in the form EC43(5) and EC4 were injected intravenously into C6-deficient, C3-depleted and normal rabbits. EC4 survived normally during the period of observation, whereas EC43(5) were removed exponentially (t_½:1½–4 min) from the circulation at sites in the reticuloendothelial system. In the liver, the main site of sequestration, EC43(5) attached to Kupffer cells, where some were immediately ingested. With time, unphagocytosed EC43(5) returned to the circulation at a slow exponential rate (t_½:25–100 min), apparently as damaged, spherocytic cells. It is suggested that the return of EC43(5) to the circulation from sites of attachment on fixed macrophages is due to the progressive in vivo inactivation of fixed-C3. It would therefore appear that the presence of fixed C3 in an active form is essential for the non-lytic sequestration and damage of red cells which have been exposed to IgM cold antibody.

The in vivo metabolism of radioiodinated cold agglutinins of anti-I specificity

1. The metabolism of six purified and radioiodinated cold agglutinins has been studied in five patients with chronic cold haemagglutinin disease and in six normal controls. Two of the patients showed overt haemolysis at the time of this study and all had complement components adsorbed to the surface of their red cells.

2. The mean fractional catabolic rate (FCR) of the cold agglutinins, studied in the patients from whom they were isolated (14·5%/day), was similar to the mean FCR of the same cold agglutinins in normal controls (15·6%/day) and there was no correlation between the FCR and the presence of haemolysis. Exposure to cold with a concomitant increase in haemolysis during the course of one of these studies had no effect on the catabolic rate of the cold agglutinin.

3. Individual values for the FCR ranged from 10·8 to 19·4%/day (corresponding to half-lives of 4·9–7·8 days) and appeared to be characteristic for each recipient. When two different cold agglutinins were studied simultaneously in the same subject their catabolism was virtually identical.

4. Untreated patients with chronic cold haemagglutinin disease were calculated to be synthesizing IgM at approximately ten times the normal rate. The fall in serum IgM concentration and agglutinin and haemolysin titres, following treatment with alkylating agents, appeared to be due to a diminution in the rate of synthesis and not due to increased catabolism.

5. ‘7S’ subunits of one of the cold agglutinins, which retained cold haemagglutinating activity, were rapidly catabolized in a normal subject.

CHLOROPLAST DEVELOPMENT AND ULTRESTRUCTURE IN THE FRESHWATER RED ALGA BATRACHOSPERMUM(1)

Chloroplast development and ultrastructure of the freshwater red alga Batrachospermum moniliforme are described. Chloroplasts develop from proplastids which have a double-membraned chloroplast envelope and a parallel double-membraned outer photo-synthetic lamella. Of these 2 double-membraned structures of the proplastid, only the outermost pho-tosynthetic lamella functions in production of further lamellae. The mature chloroplast consists of 2 or more concentric lamellae and a variable number of nonconcentric lamellae. These lamellae are not dense, uninterrupted sheets as described for other red algae, but are largely constructed of tubules, lying side by side, that form interrupted lamellar sheets. The possible physiological significance of lamellar interruptions in providing path-ways for movement of materials in the chloroplast stroma is discussed.

Penicillin-induced haemolytic anaemia

The case histories of two patients with penicillin-induced haemolytic anaemia are presented. One had received 20 mega units a day for 18 days, the other had received 20 mega units a day for two days and then 12 mega units a day for 25 days, before the haemolytic anaemia was diagnosed. Both had previously had courses of penicillin. A strongly positive direct antiglobulin reaction which appeared to be mainly due to IgG antibody was one of the main diagnostic features, and free IgG antipenicillin antibody was found in the serum of both patients. The haemolysis appeared to Lessen as soon as the drug was stopped, and the direct antiglobulin test became negative in 66-77 days.Twelve additional reported cases are reviewed. All had received high doses of penicillin and all had had penicillin previously. The lowest dose recorded was 10 mega units a day for 26 days. The incidence of anti-penicillin antibodies in a hospital population is given, and the mechanism of this type of haemolytic anaemia is discussed. Penicillin-induced haemolytic anaemia should be suspected in any patient receiving penicillin in high doses in whom there is a fall in the haemoglobin level.