Demography of serum immunoglobulins: differences in IgG and IgM levels in two normal Mexican adult populations

1. The three major immunoglobulins were quantitatively determined in the serum of 112 healthy Mexico City residents by the single radial immunodiffusion method.

2. Mean levels of IgG and particularly of IgM were unusually low as compared to (a) mean levels reported from elsewhere, (b) a group of thirty-eight healthy residents of Acapulco, Mexico of similar racial background and income and (c) a ‘British’ standard reference serum.

3. It is suggested that low IgG and IgM levels in Mexico City residents may be related to its high altitude.

4. Diminished immunoglobulin levels, particularly those of IgM, might be a compensatory mechanism for the increase in blood viscosity caused by high altitude erythrocytosis.

The range and specificity of antinuclear antibodies in systemic lupus erythematosus

Antibodies to nine calf thymus nuclear antigens were sought by complement fixation methods in twenty-four sera from sixteen patients with systemic lupus erythematosus. These antigens included whole nuclei, native and heat denatured DNA, particulate and soluble nucleoprotein and Sm antigen. Soluble antigens were also tested by tanned red-cell agglutination tests. A wide variation in the presence and titres of antibodies to these various antigens was found in the sera studied even when from the same patient but at different times. To further test the range and specificity of antinuclear antibodies in SLE, nineteen ribonucleosides, nucleotides and monophosphoric dinucleotides were coupled to human serum albumin and used as antigens in precipitin studies. A wide variation of reactivity was also found in each serum. Exquisite specificity became apparent, capable of reacting with a nucleoside but not with the corresponding nucleotide or vice versa, with a dinucleotide but not with the nucleotides or nucleosides which it contained, with a given dinucleotide but not with the opposite sequence.

Antinuclear antibodies in systemic lupus are, therefore, markedly heterogeneous. Those to a `single' antigen such as DNA may be directed to antigenic sites which may variously be at the bases, single or in sequence, at the site of union of base and sugar–phosphate moiety, at the backbone of deoxyribophosphate or actually dependent on the secondary structure.

Antibodies to nucleoprotein and to hydrazide-altered soluble nucleoprotein in tuberculous patients receiving isoniazid

Antibodies to calf thymus nuclei, nucleoprotein, DNA, soluble nucleoprotein and hydrazide (hydrallazine and isoniazid)-altered nucleoprotein were investigated by a standard complement-fixation method in 214 tuberculous patients receiving isoniazid. Findings were compared to those on thirty-seven sera from lupus patients receiving neither steroids nor immunosuppressants and on sixty-six sera from normal controls.

The incidence of antibodies to all antigens studied except DNA was significantly higher in isoniazid-treated tuberculous patients than in the normal controls, but lower than in the lupus patients. Unlike lupus there were no detectable DNA antibodies in the tuberculous or in the control sera. Antibodies to nucleoprotein (soluble and insoluble) and particularly to hydrazide-altered nucleoprotein were the most frequently found in the isoniazid-treated tuberculous patients. In general, antinuclear antibodies were more frequent in the isoniazid-treated tuberculous female than in the male; in the adult than in the child.

It is suggested that hydrazides may cause in vivo similar alteration of nucleoprotein to that which they cause in vitro. Hydrazide-altered nucleoprotein probably elicits the production of antinuclear antibodies which in turn may activate systemic lupus erythematosus in otherwise predisposed individuals.