Antimycobacterial Antibodies in Pleural Effusions: DISCUSSION

8 Mar

Pleural Effusions

The optical density method is commonly used to express ELISA data in the field of mycobacterial disease; we used a similar technique (reflectance densitometry) to express immunoblotting data.

In this work, we tried to demonstrate the interest in adjusting immunoglobulin concentrations before testing the samples. Moreover, we think that titration of specific antibodies allows better evaluation of the response than comparisons of results obtained using a single dilution of serum samples.

Anti-P32 IgG and IgA were found in the serum of the nontuberculous patients, but the titers measured were lower than those observed in tuberculous pa­tients. The higher titer was noted in the patient who presented with severe associated pulmonary involve­ment.

We previously reported an anti-P32 serum humoral response in IgG and IgA classes which enabled us to discriminate between tuberculous patients and non­tuberculous subjects. The higher levels ere measured in patients with severe disease. As in all previous studies concerning serologic studies in mycobacterial infections, specific antibodies were detected in unin­fected subjects’ serum, but levels were lower than those measured using the PPD as antigen suggesting that the P32 was more specific of mycobacteria.

In fact, P32, the 85A component of the heterogenous 85 complex in the BCG reference system, also elicits a detectable cellular response in the infected patients. The P32 seems to be restricted to mycobacterial species and more precisely to Mycobacterium tuber­culosis, Mycobacterium bovis, Mycobacterium kansa- sii, and Mycobacterium avium.

Only a few studies have been performed until now in the field of local humoral antimycobacterial immu­nity in tuberculous diseases. The determination of the presence of specific antibodies has been essentially used in an attempt to establish the diagnosis of tuberculous meningitis. We demonstrated recently the interest of comparing local and systemic humoral response in order to diagnose such a mycobacterial meningeal involvement.

T-lymphocytes suggest­ing a compartmentalization of the pleural spaces. Only Shim et al studied the pleural antibody reactivity without comparing serologic and local humoral re­sponses.

In our study, total serum immunoglobulin levels varied from one patient to another and were higher in tuberculous patients than in the others. More impor­tant individual variations were observed at the local

level so that we adjusted the immunoglobulin concen­trations before testing the samples in order to compare their specific reactivities. The results show the local accumulation of specific immunoglobulins, and as far as diagnosis is concerned, the better discrimination is obtained between nontuberculous and tuberculous patients when studying pleural fluids. We thus empha­size the interest in studying the local humoral response in well standardized conditions for the diagnosis of pleural tuberculous disease.