Scand J Haematol(l979) 22, 141-144
Heat Production by Lymphocytes in Chronic Lymphocytic Leukaemia L. BRANDT,~ J. IKOMI-KUMM,3 M. MONTI~ & I. WADSO:'
3
Department of Oncology and 2 Department of Internal Medicine, University Hospital, Lund and Thertnochernistry Laboratory, Chemical Center, University of Lund, Lund, Sweden
Using microcalorimeters of the thermopile conduction type heat production was measured in lymphocytes from peripheral blood in 8 normals and 10 patients with chronic lymphocytic leukaemia (CLL). The heat production per CLL lymphocyte was lower (1.8 pW/cell) than that found in normal lymphocytes (2.6 pW/cell). Due to the high numbers of lymphocytes in the peripheral blood the estimated heat production of the intravascular lymphocyte pool in CLL was considerably higher than in normals. Since the circulating lymphocytes constitute a minute fraction of the total lymphoid mass in CLL it is suggested that the accumulation of metabolically active lymphocytes in blood and tissues may explain the common clinical signs of hypermetabolism in this disease. The results also indicate that calorimetry may be a useful technique for metabolic studies in suspensions of malignant cells. Key words: CLL - heat production - hypermetabolism - lymphocytes
Accepted for publication December 2, 1978 Correspondence to: Dr. M. Monti, Department of Internal Medicine, University Hospital, S-22185 Lund, Sweden
Sweating, loss of weight and an increased basal metabolic rate unassociated with hyperthyroidism are often found in CLL. However, the mechanisms bringing about the hypermetabolic state are incompletely known (Hansen 1973). Calorimetry has lately been applied to the investigation of metabolic processes in blood cells and has proven to be a suitable technique for measuring the total metabolic activity of a cell population (Monti & Wadso 1978). In the present study the heat pro-
duction in lymphocytes has been measured in normals and in patients with CLL. An attempt has been made to evaluate the metabolic activity of the lymphocyte mass in CLL. MATERIALS AND METHODS Patients and controls 10 patients with elevated WBC counts, 13-210 x 109/1, due t o typical CLL were selected without regard t o H b concentration, platelet counts, degree of lymph node enlargement or spleen size.
142
L. BRANDT, J. IKOMI-KUMM, M. MONTI & I. WADSO
Untreated patients as well as patients under treatment with alkylating agents were included. 8 healthy volunteers served as controls. Preparation of samples Lymphocytes were isolated from defibrinated whole blood by density gradient centrifugation in Ficoll-Paque medium (Pharmacia, Uppsala) by the method of Boyum (1968). Contaminant phagocytizing cells were removed by incubating the lymphocyte suspension in plasma with iron filings at 37O C under rotation !h h and removing the iron and adherent phagocytic cells with a magnet. The lymphocytes were washed twice in phosphate buffer, pH 7.40 and resuspended in autologous plasma which had been recentrifuged at 8,000 x g. The lymphocyte concentration was adjusted t o about 4 x lo9 cellsA and counting of lymphocytes in each final cell suspensions was performed in a Biirker chamber just before calorimetric measurements. The pH of the final lymphocyte suspension taken directly from the calorimeter ampoule at the end of 1 h incubation at 37O C was determined using a Radiometer capillary electrode p H meter. Defibrination of whole blood prior t o density gradient centrifugation, high speed centrifugation of plasma and washing procedure reduced platelet contamination t o less than 3 x 106 celldl. Red blood cell contamination was less than 20 x 106 celldl. No attempts were made t o destroy contaminant red blood cells as they were unlikely t o contribute appreciably to the measured heat effect and more likely to provide a useful aerobic milieu for the lymphocytes during calorimetric measurements. Lymphocyte preparation and cell counts were completed in 4 t o 5 h and all preparation procedures were carried out at 2 5 O C except where stated otherwise. Calorimetry Microcalorimeters of the thermopile heat conduction type were used. Samples were enclosed in a 1 ml stainless steel ampoule. The determinations were carried out under static conditions in the type of instrument described in previous reports (Monti & Wadso 1973, Bandmann et al 1975). The reported heat effects were calculated from readings taken exactly 1 h after the cell suspension had been incubated under static conditions in the calorimeter.
RESULTS
The mean heat production was 2.6 f 0.5 (SD) pW/cell in the group of healthy subjects and 1.80 ?E 0.5 pW/cell in the CLL group (Figure 1) at a pH of 7.78 ? 0.07 and 7.74 f 0.08 respectively. The difference in heat production is significant (P < 0.005). DiSCUSSION
The heat production by lymphocytes in the group of healthy subjects was found to be
4.0
3.0
.. .*
2.0
. .
.. . ..
0 .
0 .
1.0
0 NORMAL
CLL
Figure 1. Heat effects of lymphocytes (pW/cell) suspended in plasma. Normal subjects and patients with CLL.
HEAT PRODUCTION BY CLL LYMPHOCYTES
in fairly good agreement with the results previously obtained in a group of normal persons, 2.2 f 1.4 (SD) (Bandmann et a1 1975). In the CLL group the heat production per lymphocyte was found to be subnormal, indicating a decreased metabolic activity in these cells. This result is in line with the findings of Brody et a1 (1969) who demonstrated an impaired pentose phosphate shunt and a decreased glycolytic acticity in CLL lymphocytes. The reported hypometabolism of the lymphocytes probably does not reflect a generalised reduction of cellular metabolic activity in CLL. Thus a normal and even elevated heat production has been found in red cells (Monti, to be published). Using the mean values for the heat production per lymphocyte obtained in the present study, calculations of the heat production of the intravascular lymphocyte pool in a healthy subject with a peripheral blood lymphocyte count of 2.0 x 109/1 amount to some 0.03 W. In CLL with a lymphocyte count as high as 200 x lo9/] the corresponding value is 1.80 W i.e. approximately 60 times higher. There is evidence that in CLL the intravascular pool of lymphocytes is part of a lymphocyte recirculating pool (LRP) (Schiffer 1968, Stryckmans et a1 1977). According to data given by Stryckmans et a1 (1977) it can be estimated that the LRP in a CLL patient with a blood lymphocyte count of 200 X lo9/] is about 3.5 X 1Olo lymphocytes per kg body weight. From our data on the heat production by the leukaemic lymphocytes it can be calculated that in such patient weighing 70 kg the LRP will produce heat corresponding to about 4 w. There is evidence (Schiffer 1968) that the LRP constitutes only a minute fraction of the total lymphoid mass in CLL and that another compartment, the tissue lympho-
143
cytes, may constitute the major tumour mass. The heat production of the tissue lymphocytes in CLL is therefore probably several times that calculated for the LRP. The total heat production of the normal human body is about 100 W (Kleiber 1961). The accumulation of lymphocytes in various tissues in CLL therefore means a significant increase in the metabolitically active cells contributing to the hypermetabolic state often seen in CLL. Such concept is supported by the finding of a reduction of the basal metabolic rate following splenectomy in CLL patients with considerable splenomegaly (Videbaek et a1 1976). In order to investigate specific cell properties calorimetry has to be combined with other analysis. However, calorimetry has been found to be a useful method to determine the total metabolic activity of various cell populations including red cells, granulocytes, platelets and lymphocytes (Spink & Wadso 1976, Monti & Wadso 1978). In the present work calorimetry has been applied to the study of malignant cells. Although such cells are most easily obtained from the peripheral blood in malignant haematologic conditions it is conceivable that calorimetry can be applied to tumour cells obtained through fineneedle aspiration biopsy or to excised material. ACKNOWLEDGEMENTS This work has been supported by a grant from the Torsten and Elsa Segerfalks Research Fund. REFERENCES Bandmann U, Monti M & Wadso I (1975) Microcalorimetric measurements of heat prduction in whole blood and blood cells of normal persons. Scund I CIin Lab Invest 35, 121-27.
144
L. BRANDT, J. IKOMI-KUMM, M. MONTI & I. WADS0
Brody J I, Oski F A & Singer D E (1969) Impaired pentose phosphate shunt and decreased glycolytic activity in lymphocytes of chronic lymphocytic leukemia. Metabolic pathway ... ? Blood 34, 421-29. Boyum A (1968) Separation of leukocytes from blood and bone marrow. Scand J CIin Lab Invest 21, Suppl 97. Hansen M M@rk (1973) Chronic lymphocytic leukaemia. Clinical studies based on 189 cases followed for a long time. Scand J Haematol, Suppl no 18, pp 102-03. Kleiber M (1961) The fire of life. John Wiley & Sons, Inc., New York. Monti M & Wadso I (1973) Microcalorimetric measurements of heat production in human erythrocytes. I. Normal subjects and anemic patients. Scand J Clin Lab Invest 32, 47-54.
Monti M & Wadso I (1978) Calorimetric studies on blood cells. In M N Jones (ed) Biochemical thermodynamics (in press). Elsevier Scientific Publishing Company, London. Schiffer L M (1968) Kinetics of chronic lymphocytic leukemia. Ser Huematol I, 3, 3-23. Spink C & Wadso I (1976) Calorimetry as an analytical tool in biochemistry and biology. In D Glick (ed) Methods in biochemical analysis, 23, 1-159. Wiley-Interscience. Stryckmans P A, Debusscher L & Collard E (1977) Cell kinetics in chronic lymphocytic leukaemia (CLL). CIin Haematol 6 , 159-67. Videbaek Aa, Christensen B E & Hansen M M (1976) Splenectomy in chronic lymphocytic leukemia (CLL). The 16th International C m gress of Haematology, Kyoto. Abstract 4-103.
Heat Production by Lymphocytes in Chronic Lymphocytic Leukaemia L. BRANDT,~ J. IKOMI-KUMM,3 M. MONTI~ & I. WADSO:'
3
Department of Oncology and 2 Department of Internal Medicine, University Hospital, Lund and Thertnochernistry Laboratory, Chemical Center, University of Lund, Lund, Sweden
Using microcalorimeters of the thermopile conduction type heat production was measured in lymphocytes from peripheral blood in 8 normals and 10 patients with chronic lymphocytic leukaemia (CLL). The heat production per CLL lymphocyte was lower (1.8 pW/cell) than that found in normal lymphocytes (2.6 pW/cell). Due to the high numbers of lymphocytes in the peripheral blood the estimated heat production of the intravascular lymphocyte pool in CLL was considerably higher than in normals. Since the circulating lymphocytes constitute a minute fraction of the total lymphoid mass in CLL it is suggested that the accumulation of metabolically active lymphocytes in blood and tissues may explain the common clinical signs of hypermetabolism in this disease. The results also indicate that calorimetry may be a useful technique for metabolic studies in suspensions of malignant cells. Key words: CLL - heat production - hypermetabolism - lymphocytes
Accepted for publication December 2, 1978 Correspondence to: Dr. M. Monti, Department of Internal Medicine, University Hospital, S-22185 Lund, Sweden
Sweating, loss of weight and an increased basal metabolic rate unassociated with hyperthyroidism are often found in CLL. However, the mechanisms bringing about the hypermetabolic state are incompletely known (Hansen 1973). Calorimetry has lately been applied to the investigation of metabolic processes in blood cells and has proven to be a suitable technique for measuring the total metabolic activity of a cell population (Monti & Wadso 1978). In the present study the heat pro-
duction in lymphocytes has been measured in normals and in patients with CLL. An attempt has been made to evaluate the metabolic activity of the lymphocyte mass in CLL. MATERIALS AND METHODS Patients and controls 10 patients with elevated WBC counts, 13-210 x 109/1, due t o typical CLL were selected without regard t o H b concentration, platelet counts, degree of lymph node enlargement or spleen size.
142
L. BRANDT, J. IKOMI-KUMM, M. MONTI & I. WADSO
Untreated patients as well as patients under treatment with alkylating agents were included. 8 healthy volunteers served as controls. Preparation of samples Lymphocytes were isolated from defibrinated whole blood by density gradient centrifugation in Ficoll-Paque medium (Pharmacia, Uppsala) by the method of Boyum (1968). Contaminant phagocytizing cells were removed by incubating the lymphocyte suspension in plasma with iron filings at 37O C under rotation !h h and removing the iron and adherent phagocytic cells with a magnet. The lymphocytes were washed twice in phosphate buffer, pH 7.40 and resuspended in autologous plasma which had been recentrifuged at 8,000 x g. The lymphocyte concentration was adjusted t o about 4 x lo9 cellsA and counting of lymphocytes in each final cell suspensions was performed in a Biirker chamber just before calorimetric measurements. The pH of the final lymphocyte suspension taken directly from the calorimeter ampoule at the end of 1 h incubation at 37O C was determined using a Radiometer capillary electrode p H meter. Defibrination of whole blood prior t o density gradient centrifugation, high speed centrifugation of plasma and washing procedure reduced platelet contamination t o less than 3 x 106 celldl. Red blood cell contamination was less than 20 x 106 celldl. No attempts were made t o destroy contaminant red blood cells as they were unlikely t o contribute appreciably to the measured heat effect and more likely to provide a useful aerobic milieu for the lymphocytes during calorimetric measurements. Lymphocyte preparation and cell counts were completed in 4 t o 5 h and all preparation procedures were carried out at 2 5 O C except where stated otherwise. Calorimetry Microcalorimeters of the thermopile heat conduction type were used. Samples were enclosed in a 1 ml stainless steel ampoule. The determinations were carried out under static conditions in the type of instrument described in previous reports (Monti & Wadso 1973, Bandmann et al 1975). The reported heat effects were calculated from readings taken exactly 1 h after the cell suspension had been incubated under static conditions in the calorimeter.
RESULTS
The mean heat production was 2.6 f 0.5 (SD) pW/cell in the group of healthy subjects and 1.80 ?E 0.5 pW/cell in the CLL group (Figure 1) at a pH of 7.78 ? 0.07 and 7.74 f 0.08 respectively. The difference in heat production is significant (P < 0.005). DiSCUSSION
The heat production by lymphocytes in the group of healthy subjects was found to be
4.0
3.0
.. .*
2.0
. .
.. . ..
0 .
0 .
1.0
0 NORMAL
CLL
Figure 1. Heat effects of lymphocytes (pW/cell) suspended in plasma. Normal subjects and patients with CLL.
HEAT PRODUCTION BY CLL LYMPHOCYTES
in fairly good agreement with the results previously obtained in a group of normal persons, 2.2 f 1.4 (SD) (Bandmann et a1 1975). In the CLL group the heat production per lymphocyte was found to be subnormal, indicating a decreased metabolic activity in these cells. This result is in line with the findings of Brody et a1 (1969) who demonstrated an impaired pentose phosphate shunt and a decreased glycolytic acticity in CLL lymphocytes. The reported hypometabolism of the lymphocytes probably does not reflect a generalised reduction of cellular metabolic activity in CLL. Thus a normal and even elevated heat production has been found in red cells (Monti, to be published). Using the mean values for the heat production per lymphocyte obtained in the present study, calculations of the heat production of the intravascular lymphocyte pool in a healthy subject with a peripheral blood lymphocyte count of 2.0 x 109/1 amount to some 0.03 W. In CLL with a lymphocyte count as high as 200 x lo9/] the corresponding value is 1.80 W i.e. approximately 60 times higher. There is evidence that in CLL the intravascular pool of lymphocytes is part of a lymphocyte recirculating pool (LRP) (Schiffer 1968, Stryckmans et a1 1977). According to data given by Stryckmans et a1 (1977) it can be estimated that the LRP in a CLL patient with a blood lymphocyte count of 200 X lo9/] is about 3.5 X 1Olo lymphocytes per kg body weight. From our data on the heat production by the leukaemic lymphocytes it can be calculated that in such patient weighing 70 kg the LRP will produce heat corresponding to about 4 w. There is evidence (Schiffer 1968) that the LRP constitutes only a minute fraction of the total lymphoid mass in CLL and that another compartment, the tissue lympho-
143
cytes, may constitute the major tumour mass. The heat production of the tissue lymphocytes in CLL is therefore probably several times that calculated for the LRP. The total heat production of the normal human body is about 100 W (Kleiber 1961). The accumulation of lymphocytes in various tissues in CLL therefore means a significant increase in the metabolitically active cells contributing to the hypermetabolic state often seen in CLL. Such concept is supported by the finding of a reduction of the basal metabolic rate following splenectomy in CLL patients with considerable splenomegaly (Videbaek et a1 1976). In order to investigate specific cell properties calorimetry has to be combined with other analysis. However, calorimetry has been found to be a useful method to determine the total metabolic activity of various cell populations including red cells, granulocytes, platelets and lymphocytes (Spink & Wadso 1976, Monti & Wadso 1978). In the present work calorimetry has been applied to the study of malignant cells. Although such cells are most easily obtained from the peripheral blood in malignant haematologic conditions it is conceivable that calorimetry can be applied to tumour cells obtained through fineneedle aspiration biopsy or to excised material. ACKNOWLEDGEMENTS This work has been supported by a grant from the Torsten and Elsa Segerfalks Research Fund. REFERENCES Bandmann U, Monti M & Wadso I (1975) Microcalorimetric measurements of heat prduction in whole blood and blood cells of normal persons. Scund I CIin Lab Invest 35, 121-27.
144
L. BRANDT, J. IKOMI-KUMM, M. MONTI & I. WADS0
Brody J I, Oski F A & Singer D E (1969) Impaired pentose phosphate shunt and decreased glycolytic activity in lymphocytes of chronic lymphocytic leukemia. Metabolic pathway ... ? Blood 34, 421-29. Boyum A (1968) Separation of leukocytes from blood and bone marrow. Scand J CIin Lab Invest 21, Suppl 97. Hansen M M@rk (1973) Chronic lymphocytic leukaemia. Clinical studies based on 189 cases followed for a long time. Scand J Haematol, Suppl no 18, pp 102-03. Kleiber M (1961) The fire of life. John Wiley & Sons, Inc., New York. Monti M & Wadso I (1973) Microcalorimetric measurements of heat production in human erythrocytes. I. Normal subjects and anemic patients. Scand J Clin Lab Invest 32, 47-54.
Monti M & Wadso I (1978) Calorimetric studies on blood cells. In M N Jones (ed) Biochemical thermodynamics (in press). Elsevier Scientific Publishing Company, London. Schiffer L M (1968) Kinetics of chronic lymphocytic leukemia. Ser Huematol I, 3, 3-23. Spink C & Wadso I (1976) Calorimetry as an analytical tool in biochemistry and biology. In D Glick (ed) Methods in biochemical analysis, 23, 1-159. Wiley-Interscience. Stryckmans P A, Debusscher L & Collard E (1977) Cell kinetics in chronic lymphocytic leukaemia (CLL). CIin Haematol 6 , 159-67. Videbaek Aa, Christensen B E & Hansen M M (1976) Splenectomy in chronic lymphocytic leukemia (CLL). The 16th International C m gress of Haematology, Kyoto. Abstract 4-103.
