Substitute Antibiotics as known have strong effects on body tissue, these additive materials enhance host health condition, immunity status and increase body weight. Our study displays the effects of Saccharomyces cerevisiae (s. cerevisiae) and probiotic- in enhancing immune response of the host. Therefore, to explore the effects of alternative antibiotic on the histology and immunohistochemical expression on the immune organs of broilers immunized with Newcastle vaccines, sixty birds were divided randomly into 4 groups (T1-T4). T1 as a negative control, T2 immunized group with Newcastle disease virus, T3 supplemented with a mixture of Saccharomyces cerevisiae (3mg\kg) of body weight and probiotic (200g\100 litre of water) whileT4 supplemented with a mixture of these materials and vaccinated with ND. Histological sections of thymus glands were taken at 7 &35 days of the trail. Microscopic sections showed depletion, infiltration of inflammatory cell, hemorrhage as well as Hassal's corpuscle appeared in different sizes in the cortex and medulla. CD68 proteins expression was severe at 35 days in contrast to 7days that showed weak expression of these proteins' markers in all treated groups. We concluded that administration of (S. cerevisiae) and probiotic can ameliorate the immunity.