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During l-Asparaginase (l-Asp) treatment the development of specific antibodies of IgG isotype is frequently observed. In most instances elevated IgG antibodies to l-Asp activate the complement system and induce allergic reactions following l-Asp infusion. However, in some cases no adverse reactions and no activation of complement are noticed, despite the presence of elevated anti-l-Asp levels. We studied the development of specific IgG antibodies to l-Asp in different subclasses in 12 children who had produced high levels of specific IgG. Results showed that all patients had elevated levels of IgG1. In 5 cases we were able to demonstrate the development of specific IgG3 antibodies and in 1 case of IgG4 antibody. Patients with high levels of IgG3 (above 100 AU) had the highest risk for subsequent anaphylaxis. Thus, subclass-specific determination of antibodies to l-Asparaginase might improve the estimation of the risk of anaphylaxis prior to 1-Asp infusions.

Platelet function tests prior to and post intravenous gammaglobulin infusions (i.v. IgG) were performed in 20 children with acute lymphoblastic leukemia under conventional maintainance therapy. Platelet function was not influenced in 8 patients with decreased preinfusion IgG-levels. Severe platelet function defects, resembling an acquired storage pool disease, post i.v. IgG-infusion, however, were observed in 2 of 12 patients with normal preinfusion IgG-levels.

Children with acute lymphocytic leukemia received gammaglobulin replacement therapy using either one of two i.v. gammaglobulin preparations in order to reduce the frequency and severity of infections during cytostatic treatment. Sera and EDTA-plasma taken prior to each infusion and following each infusion were analyzed for several complement components and immune complexes in order to assess in vivo anticomplementary activity. Preliminary data published in this paper show only little changes in the complement system. This may be related to fact that infusions were well tolerated. IgG-levels could be raised for more than 200 mg/dl by administration of doses around 150 mg/kg body weight.

Zymosan opsonisation was determined in sera of 38 normal individuals and 20 children with acute lymphocytic leukemia (ALL). All patients underwent chemotherapy according to the CoALL 82 protocol. Intravenous gammaglobulin (ivGG) was given prophylactically to replace deficient specific antibodies. Zymosan opsonisation in normal sera ranged from 65% to 133% of a serum pool, whereas sera of children with ALL exhibited markedly decreased opsonisation ranging from 7% to 141% (of the pooled serum standard) at different times during an observation period of 20 months. No significant changes could be observed over time, neither induced by the ivGG infusion itself (short term effect) nor during the 20 months observation period (long term effect). Before ivGG therapy was initiated, a positive correlation was found between zymosan opsonisation and complement parameters (CH 50: p less than 0.01; AP 50; p less than 0.001; C3: p less than 0.05). No correlation could be noted between zymosan opsonisation and IgG concentration. Experiments with complement deficient sera clearly demonstrated the dependence of zymosan opsonisation from complement function. In contrast, sera with little or no IgG but intact complement, showed normal zymosan opsonisation. Deficient zymosan opsonisation might contribute to the immune deficiency of ALL patients. The present study suggests, that the zymosan opsonisation cannot be corrected by ivGG infusions.

Twenty-four children (2-15 years old) with acute lymphocytic leukemia (ALL) were treated intravenously with 1-Asparaginase (1-Asp) isolated from E coli at a dose of 3,000 U/kg body weight four times every third day as part of a standard chemotherapy protocol. Sera of patients were obtained prior to each infusion, immediately following each infusion, and at defined intervals (2, 4, 12, 24, 36, and 48 hours postinfusion) and assayed for 1-Asp enzymatic activity.1-Asp antigen, and anti-1-Asp antibodies. Results indicate that the in-vivo elimination half-life of 1-Asp activity in patients with no demonstrable specific antibody is approximately 5.5 hours. Half-life of enzymatic activity in patients with a moderately high level of specific antibodies (pre-infusion) was prolonged (approximately 7.0 hours) in comparison to the group with no specific antibodies. In patients with very high levels of specific antibodies several infusions could not be completed because of apparent anaphylactic reactions. In-vitro studies showed that experimental immune complexes made of 1-Asp and the IgG-fraction of a rabbit-anti-1-Asp antibody under conditions of antigen excess still exhibit enzymatic activity. On the basis of this observation we conclude that specific antibodies to 1-Asp in vitro and, most likely, in vivo do not inactivate the drug but may lead to either delayed elimination of enzyme activity or, in the presence of high levels of specific antibodies, anaphylactic reaction.

L-Asparaginase (l-Asp) is widely used as an effective drug against childhood and adult acute lymphoblastic leukemia (ALL). However, it is immunogenic in humans and may lead to hypersensitivity reactions. The immunological basis of these reactions is not clear. Since the presence of l-Asp specific IgG-antibodies seems to correlate better with clinical reactions than IgE-antibodies and IgG-antibodies are known to be able to fix and activate the complement system, we speculated that the mechanism of anaphylaxis may be complement- rather than IgE-mediated. We analyzed 24 children with ALL (age 2-15 yr) for changes in the complement system during l-Asp infusions. Chemotherapy was administered according to the CoALL 82 protocol which is derived from the CoALL 80 protocol recently published. The formation of specific antibodies of IgM and IgG classes against l-Asp was monitored by a solid phase ELISA. The immunological responsiveness of individual patients varied over a wide range but both types of antibodies were induced. Anaphylactic reactions were observed on eight occasions in eight children. The infusions in the remaining 16 patients were tolerated without clinical reactions. Significant activation of complement was demonstrated in seven of eight reaction occasions and in none of the occasions without reactions. The most important complement activation parameter monitored was the C3 split product C3d measured in EDTA-plasma. We conclude that anaphylaxis to l-Asp in patients with ALL can be explained in most instances on the basis of complement activation induced by the formation of immune complexes of l-Asp and specific antibodies of IgM and IgG classes.

The efficiency and toxicity of E. coli-L-Asparaginase coupled to polyethyleneglycol (PEG-ASP) was investigated in 5 patients with second relapse of acute lymphoblastic leukemia. PEG-ASP was administered at a dose of 2000 U/m2 as infusion over 2 hrs. every 2 weeks. Following an initial single agent phase, PEG-ASP was combined with prednisone, vincristine, adriamycin and methotrexate i.t. Following induction, all 5 patients were in third remission. The remissions lasted from 3 to 9 months, median 4 months. The toxicity was transient and mild. Also in patients sensitized against native L-Asparaginase no anaphylactic reactions were observed.

The influence of intravenous gammaglobulin infusions (ivGG) on hemolytic complement function and the concentration of serum C3 and its split product C3dg was studied in 20 children with acute lymphocytic leukemia (ALL) undergoing ivGG prophylaxis. IvGG was infused once monthly over a period of 20 months using two different preparations commercially available. Serum and EDTA-plasma were collected before initiation of ivGG therapy (time 1), after 10 and 20 months (time 2 and 3), before and immediately after the infusions. IvGG was infused in connection with chemotherapy (according to the CoAll 82 protocol). 16 of 60 sera collected prior to infusions contained less than 700 mg/dl IgG. Mean IgG concentrations could be raised to 198 mg/dl (time 1), 219 mg/dl (time 2), and 213 mg/dl (time 3), respectively. -CH 50 prior to infusions was below normal in 15 of 59 sera, afterwards in 25 of 59 sera. AP 50 before (after) infusions was decreased in 29 of 59 (36 of 60) sera, C3 in 18 of 60 (24 of 60) sera. C3dg was slightly elevated in one EDTA-plasma prior to ivGG infusions and in 5 of the plasmas following infusions. IvGG infusions resulted in a significant loss of hemolytic activity of serum complement (p less than 0.01, F-test). The effect was more profound if IgG concentrations before infusions were less than 700 mg/dl, but this was true for only one of the two used ivGG preparations. The long term follow up over two years showed no significant changes of complement functions (F-test), indicating complete recovery of complement function from short term anticomplementary effects.