Letters to the editor
Intrathecal synthesis of IgM in early multiple sclerosis Lolli and colleagues’ (1) finding of intrathecal IgM synthesis in 42% of patients with early multiple sclerosis (MS) corroborates my earlier observations (2, 3). Moreover, their proposal to include the determination of IgM in the analysis of CSF in patients presenting with initial MS is in accordance with my previous suggestion (4). The authors (1) determined intrathecal synthesis of IgM by calculating the IgM index which is an empirical formula based upon physiologic principles governing transudation of albumin and IgM across the blood-cerebrospinal fluid (CSF) barriers. The IgM index refers CSF/serum ratio of IgM to that of albumin to correct for transudation across the barriers. However, such correction may be insufficient, since the passage of proteins is clearly dependent on their size. IgM, a macroglobulin with an extremely large hydrodynamic size, penetrates intact bloodCSF barriers with difficulty and is likely to give misleading results in the presence of barrier damage. I have established that the detection of oligoclonal IgM bands in CSF ( 5 ) is more reliable than IgM index in relating to intrathecal IgM synthesis (6). I have also been conducting a prospective study (4) to evaluate the predictive value of CSF oligoclonal IgM bands and high IgM index in patients with acute monofocal lesions of brainstem or spinal cord for subsequent development of MS. Paired CSF and serum samples were obtained from 48 patients who presented with unequivocal acute isolated syndromes of brainstem or spinal cord. None had transverse myelitis, vascular lesions, or intrinsic tumours at presentation and all those with spinal cord syndromes had myelography to exclude compressive lesions. Results after 30 months’ follow up demonstrated that CSF oligoclonal IgM bands were more reliable than high values of IgM index in predicting future development of clinically definite MS (Table 1). It is noteworthy that my reported findings on the detection and distribution of oligoclonal IgM bands in MS (2, 3, 5 , 6) have been corroborated by an independent group (7) using agarose isoelectric focusing. Therefore, it is suggested that studies of intrathecal IgM synthesis in initial MS should include
456
Table 1. Relationship of CSF IgM oligoclonal bands (OC) and IgM index at presentation to the outcome after 30 months of follow-up Outcome on follow-up
feature at presentation
CSF-OC IgM positive and high IgM Indexa CSF-OC IgM positive and normal IgM Index CSF-OC IgM negative and high IgM Index CSF-OC IgM negative and normal IgM Index All patients a
Total No.
MS
Non-MS
Ongoing follow-up
18
17
0
1
8
4
0
4
7
0
3b
4
12
0
2c
10
45
21
5
19
Upper limit of IgM index in normal reference population is 0.068. Two patients had cerebrovascular brainstem disease and a third patient had pontine tumour. Intrinsic spinal cord tumours.
the detection of oligoclonal IgM bands. High IgM index values alone may yield misleading data especially in the presence of blood-CSF barrier dysfunction. Oligoclonal IgM bands are not particularly sensitive to changes in barrier permeability and are relatively not labour-intensive. References 1. LOLLIF, SIRACUSA G, AMATOM et al. Intrathecal synthesis of free immunoglobulin light chains and IgM in initial multiple sclerosis. Acta Neurol Scand 1991: 83: 239-243. 2. SHARIEFMK, THOMPSON EJ. Immunoglobulin M in the cerebrospinal fluid: An indicator of recent immunological stimulation. J Neurol Neurosurg Psych 1989: 52: 949-953. 3. SHARIEFMK, THOMPSON EJ. Intrathecal immunoglobulin M synthesis in multiple sclerosis. Relationship with clinical and cerebrospinal fluid parameters. Brain 1991: 114: 181-195. 4. SHARIEF MK, THOMPSON EJ. The predictive value of intrathecal immunoglobulin synthesis and MRI in acute isolated syndromes for the subsequent development of multiple sclerosis. Ann Neurol 1991: 29: 147-151. 5. SHARIEFMK, KEIR G, THOMPSON EJ. Glutaraldehydeenhanced immunofixation: A sensitive new method for detecting oligoclonal immunoglobulin M. J Neuroimmunol 1989: 23: 149-156. 6. SHARIEFMK, KEIR G, THOMPSON EJ. Intrathecal synthesis of IgM in neurological diseases: a comparison between
Letters to the editor detection of oligoclonal bands and quantitative estimation. J Neurol Sci 1990: 96: 131-142. 7. GILESPD, WROESJ. Cerebrospinal fluid oligoclonal IgM in multiple sclerosis: analytical problems and clinical limitations. Ann Clin Biochem 1990: 27: 199-207.
M.K. Sharief Institute of Neurology London Reply
We are aware of the important study from Dr. Sharief (1) that expands and validates our results. However, we and others repeatedly tried to detect oligoclonal IgM band in the cerebrospinal fluid (CSF) of multiple sclerosis patients, with unsuccessful results in labour-intensive experiments, and the common observations of unspecific reactions (2). Furthermore, the sensitive method developed from Gallo et al. only occasionally detected CSF IgM oligoclonal bands in multiple sclerosis (3), so that there is no generally accepted interpretation of the contrasting findings. Dr. Sharief, as many others, questions the results obtained with the IgM index, especially in case of blood-brain-barrier damage. We do not agree completely with this objection. In spite of the high hydrodynamic size of IgM, many studies showed a good correlation between the IgM level in the CSF and serum of normal subjects (4, 5). We also had a good correlation between the CSF/plasma IgM ratio and the CSF/plasma albumin ratio in 57 tension headache subjects (r = 0.75, p < 0.01), suggesting that IgM physiologically penetrates the blood-brainbarrier in a way that can be compared with that of albumin (6). Sindic et al. reported only one patient with an increased IgM index in a group of 39 with miscellaneous not inflammatory neurological disorders and blood-brain-barrier damage; in the same patients, there was again a good correlation between the CSF/serum IgM ratio and the similar ratio for albumin (7). We had similar observations, with many patients with severe blood-brain-barrier damage of the not inflammatory type and a normal IgM index.
These data indicate that the IgM index, as well as the IgG and IgA indices, can adjust for the increased diffusion of IgM to the brain in presence of bloodbrain-barrier damage and it is a useful measure of intrathecal IgM synthesis. From a different point of view, only a few multiple sclerosis patients present blood-brain-barrier damage. For example, in our study, there were only borderline alterations of the blood-brain-barrier in 8 of 33 patients. For this reason we consider unlikely false interpretations of the IgM index in early multiple sclerosis.
References 1. SHARIEF MK, THOMPSON EJ. The predictive value of intrathecal immunoglobulin synthesis and MRI in acute isolated syndrome for the subsequent development of multiple sclerosis. Ann Neurol 1991: 29: 147-151. 2. CHIODIF, LINKH. Limitation of the avidin-biotin system in detection of cerebrospinal fluid IgM separated by agarose isoelectric focusing. In: NEUHOFFV, ed. Electrophoresis 84. Weinheim: Verlag-Chemie, 1984. 3. GALLOP, BRACCOF, MORARAS, TAVOLATO B. Monoclonal and oligoclonal IgM in the cerebrospinal fluid. In: LOWENTHAL A, RAUSJ, eds. Cellular and humoral immunological components of cerebrospinal fluid in multiple sclerosis. Nato ASI. Series A: Life Sciences. New York: Plenum Press, 1987: 111-116. 4. FORSBERG P, HENRIKSSON A, LINKH, OHMANS. Reference values for CSF-IgM, CSF-IgM/S-IgM ratio and IgM index, and its application to patients with multiple sclerosis and aseptic meningoencephalitis. Scand J Clin Lab Invest 1984: 44: 7-12. 5. TAKEOKA T, SHINOHARA Y, MORIK, FURUMI K. Solidphase immunofluorometric assay for quantification of CSF immunoglobulins. Determination of normal reference values. J Neurol Sci 1990: 96: 229-240. I, LINKH. Intrathecal synthesis of IgG, 6. LOLLIF, HALAWA IgA, IgM and IgD in untreated multiple sclerosis and controls. Acta Neurol Scand 1989: 80: 238-247. L, DEPREA, LATERRE EC, MAS7. SINDICCJM, CAMBIASO SON PL. The concentration of IgM in the cerebrospinal fluid of neurological patients. J Neurol Sci 1982: 55: 339-350.
Francesco Lolli Department of Neurological Sciences & Psychiatry University of Firenze
457
Intrathecal synthesis of IgM in early multiple sclerosis Lolli and colleagues’ (1) finding of intrathecal IgM synthesis in 42% of patients with early multiple sclerosis (MS) corroborates my earlier observations (2, 3). Moreover, their proposal to include the determination of IgM in the analysis of CSF in patients presenting with initial MS is in accordance with my previous suggestion (4). The authors (1) determined intrathecal synthesis of IgM by calculating the IgM index which is an empirical formula based upon physiologic principles governing transudation of albumin and IgM across the blood-cerebrospinal fluid (CSF) barriers. The IgM index refers CSF/serum ratio of IgM to that of albumin to correct for transudation across the barriers. However, such correction may be insufficient, since the passage of proteins is clearly dependent on their size. IgM, a macroglobulin with an extremely large hydrodynamic size, penetrates intact bloodCSF barriers with difficulty and is likely to give misleading results in the presence of barrier damage. I have established that the detection of oligoclonal IgM bands in CSF ( 5 ) is more reliable than IgM index in relating to intrathecal IgM synthesis (6). I have also been conducting a prospective study (4) to evaluate the predictive value of CSF oligoclonal IgM bands and high IgM index in patients with acute monofocal lesions of brainstem or spinal cord for subsequent development of MS. Paired CSF and serum samples were obtained from 48 patients who presented with unequivocal acute isolated syndromes of brainstem or spinal cord. None had transverse myelitis, vascular lesions, or intrinsic tumours at presentation and all those with spinal cord syndromes had myelography to exclude compressive lesions. Results after 30 months’ follow up demonstrated that CSF oligoclonal IgM bands were more reliable than high values of IgM index in predicting future development of clinically definite MS (Table 1). It is noteworthy that my reported findings on the detection and distribution of oligoclonal IgM bands in MS (2, 3, 5 , 6) have been corroborated by an independent group (7) using agarose isoelectric focusing. Therefore, it is suggested that studies of intrathecal IgM synthesis in initial MS should include
456
Table 1. Relationship of CSF IgM oligoclonal bands (OC) and IgM index at presentation to the outcome after 30 months of follow-up Outcome on follow-up
feature at presentation
CSF-OC IgM positive and high IgM Indexa CSF-OC IgM positive and normal IgM Index CSF-OC IgM negative and high IgM Index CSF-OC IgM negative and normal IgM Index All patients a
Total No.
MS
Non-MS
Ongoing follow-up
18
17
0
1
8
4
0
4
7
0
3b
4
12
0
2c
10
45
21
5
19
Upper limit of IgM index in normal reference population is 0.068. Two patients had cerebrovascular brainstem disease and a third patient had pontine tumour. Intrinsic spinal cord tumours.
the detection of oligoclonal IgM bands. High IgM index values alone may yield misleading data especially in the presence of blood-CSF barrier dysfunction. Oligoclonal IgM bands are not particularly sensitive to changes in barrier permeability and are relatively not labour-intensive. References 1. LOLLIF, SIRACUSA G, AMATOM et al. Intrathecal synthesis of free immunoglobulin light chains and IgM in initial multiple sclerosis. Acta Neurol Scand 1991: 83: 239-243. 2. SHARIEFMK, THOMPSON EJ. Immunoglobulin M in the cerebrospinal fluid: An indicator of recent immunological stimulation. J Neurol Neurosurg Psych 1989: 52: 949-953. 3. SHARIEFMK, THOMPSON EJ. Intrathecal immunoglobulin M synthesis in multiple sclerosis. Relationship with clinical and cerebrospinal fluid parameters. Brain 1991: 114: 181-195. 4. SHARIEF MK, THOMPSON EJ. The predictive value of intrathecal immunoglobulin synthesis and MRI in acute isolated syndromes for the subsequent development of multiple sclerosis. Ann Neurol 1991: 29: 147-151. 5. SHARIEFMK, KEIR G, THOMPSON EJ. Glutaraldehydeenhanced immunofixation: A sensitive new method for detecting oligoclonal immunoglobulin M. J Neuroimmunol 1989: 23: 149-156. 6. SHARIEFMK, KEIR G, THOMPSON EJ. Intrathecal synthesis of IgM in neurological diseases: a comparison between
Letters to the editor detection of oligoclonal bands and quantitative estimation. J Neurol Sci 1990: 96: 131-142. 7. GILESPD, WROESJ. Cerebrospinal fluid oligoclonal IgM in multiple sclerosis: analytical problems and clinical limitations. Ann Clin Biochem 1990: 27: 199-207.
M.K. Sharief Institute of Neurology London Reply
We are aware of the important study from Dr. Sharief (1) that expands and validates our results. However, we and others repeatedly tried to detect oligoclonal IgM band in the cerebrospinal fluid (CSF) of multiple sclerosis patients, with unsuccessful results in labour-intensive experiments, and the common observations of unspecific reactions (2). Furthermore, the sensitive method developed from Gallo et al. only occasionally detected CSF IgM oligoclonal bands in multiple sclerosis (3), so that there is no generally accepted interpretation of the contrasting findings. Dr. Sharief, as many others, questions the results obtained with the IgM index, especially in case of blood-brain-barrier damage. We do not agree completely with this objection. In spite of the high hydrodynamic size of IgM, many studies showed a good correlation between the IgM level in the CSF and serum of normal subjects (4, 5). We also had a good correlation between the CSF/plasma IgM ratio and the CSF/plasma albumin ratio in 57 tension headache subjects (r = 0.75, p < 0.01), suggesting that IgM physiologically penetrates the blood-brainbarrier in a way that can be compared with that of albumin (6). Sindic et al. reported only one patient with an increased IgM index in a group of 39 with miscellaneous not inflammatory neurological disorders and blood-brain-barrier damage; in the same patients, there was again a good correlation between the CSF/serum IgM ratio and the similar ratio for albumin (7). We had similar observations, with many patients with severe blood-brain-barrier damage of the not inflammatory type and a normal IgM index.
These data indicate that the IgM index, as well as the IgG and IgA indices, can adjust for the increased diffusion of IgM to the brain in presence of bloodbrain-barrier damage and it is a useful measure of intrathecal IgM synthesis. From a different point of view, only a few multiple sclerosis patients present blood-brain-barrier damage. For example, in our study, there were only borderline alterations of the blood-brain-barrier in 8 of 33 patients. For this reason we consider unlikely false interpretations of the IgM index in early multiple sclerosis.
References 1. SHARIEF MK, THOMPSON EJ. The predictive value of intrathecal immunoglobulin synthesis and MRI in acute isolated syndrome for the subsequent development of multiple sclerosis. Ann Neurol 1991: 29: 147-151. 2. CHIODIF, LINKH. Limitation of the avidin-biotin system in detection of cerebrospinal fluid IgM separated by agarose isoelectric focusing. In: NEUHOFFV, ed. Electrophoresis 84. Weinheim: Verlag-Chemie, 1984. 3. GALLOP, BRACCOF, MORARAS, TAVOLATO B. Monoclonal and oligoclonal IgM in the cerebrospinal fluid. In: LOWENTHAL A, RAUSJ, eds. Cellular and humoral immunological components of cerebrospinal fluid in multiple sclerosis. Nato ASI. Series A: Life Sciences. New York: Plenum Press, 1987: 111-116. 4. FORSBERG P, HENRIKSSON A, LINKH, OHMANS. Reference values for CSF-IgM, CSF-IgM/S-IgM ratio and IgM index, and its application to patients with multiple sclerosis and aseptic meningoencephalitis. Scand J Clin Lab Invest 1984: 44: 7-12. 5. TAKEOKA T, SHINOHARA Y, MORIK, FURUMI K. Solidphase immunofluorometric assay for quantification of CSF immunoglobulins. Determination of normal reference values. J Neurol Sci 1990: 96: 229-240. I, LINKH. Intrathecal synthesis of IgG, 6. LOLLIF, HALAWA IgA, IgM and IgD in untreated multiple sclerosis and controls. Acta Neurol Scand 1989: 80: 238-247. L, DEPREA, LATERRE EC, MAS7. SINDICCJM, CAMBIASO SON PL. The concentration of IgM in the cerebrospinal fluid of neurological patients. J Neurol Sci 1982: 55: 339-350.
Francesco Lolli Department of Neurological Sciences & Psychiatry University of Firenze
457
